The effect of duolingo application on efl students’ vocabulary learning

THE EFFECT OF DUOLINGO APPLICATIONON EFL STUDENTS’ VOCABULARY LEARNING MASTER OF EDUCATION PRINCIPLES AND METHODS IN ENGLISH LANGUAGE EDUCATION PROGRAM CODE: 8140111 SUPERVISOR 1 PH.D..

INTRODUCTION

Rationale 1 1

The rise of English as a global language highlights its essential role in today's interconnected world, serving as the main medium for communication in fields such as information, culture, science, medicine, and technology A substantial amount of esteemed literature is written in English, making proficiency in the language crucial for those seeking knowledge English language proficiency is measured through recognized international exams that evaluate listening, reading, speaking, and writing skills However, achieving fluency in these areas requires language learners to first master the vocabulary of English.

Effective communication relies heavily on a strong vocabulary, as highlighted by McCarthy (1990), making it a crucial aspect of language learning Scholars such as Basiki et al (2018) and Muddin (2018) emphasize that vocabulary may be even more important than grammar in mastering a language (Ajiko, 2020) Defined as the acquisition of words necessary for communication (Elgort and Nation, 2010), vocabulary is an essential component of language that intertwines with other linguistic elements.

Students at SMP Negeri 1 Bandar Lampung demonstrated a notable deficiency in vocabulary knowledge, as indicated by their English teacher Many students viewed vocabulary learning as unengaging, primarily due to difficulties in understanding and responding to questions in English, which led them to depend on their teachers for translations Additionally, the reliance on traditional teaching methods without the integration of multimedia tools hindered effective vocabulary instruction.

A study by Vu and Nguyen (2019) revealed that a mere fraction of Vietnamese twelfth-grade students achieved a 2,000-word vocabulary level, with rural students particularly struggling to access a diverse vocabulary Similarly, Dang (2020) found that over 90% of Vietnamese university students, who were not majoring in English, failed to master the most commonly used 2,000 words after a decade of formal English education These results underscore the alarming vocabulary deficiencies among Vietnamese learners Despite this, EFL teachers in Vietnam utilize a variety of vocabulary teaching strategies, including code-switching, translation, songs, storytelling, and innovative approaches.

Repeated writing and self-critique, coupled with limited class time, can impede effective vocabulary instruction Integrating information and communication technology (ICT) offers a promising solution to boost students' motivation for learning vocabulary.

The integration of technology in education allows teachers to create engaging online platforms for students, which can greatly improve academic performance According to Sharma, Gandhar, Sharma, and Seema (2011), utilizing technology effectively enhances learners' achievements Recent studies, such as those by Lin et al (2016), reveal that employing digital tools in English language teaching significantly increases motivation, self-confidence, and linguistic output among EFL students.

Vietnam's National Foreign Language Project, launched in 2008 and running until 2020, aims to improve English language teaching and learning by restructuring educational methods and enhancing communicative skills Recognizing that vocabulary is crucial for mastering English, the project seeks to provide students with opportunities to effectively use the language However, challenges such as limited classroom time and large class sizes hinder vocabulary acquisition, as traditional teaching methods fall short in helping students retain new words Consequently, there is a pressing need for supplementary tools that facilitate vocabulary learning outside the classroom, supporting students in their language development journey.

In today's technological era, modern technology significantly enhances education, particularly through educational applications that promote independent language exploration and learning from mistakes One notable example is Duolingo, a free app and website that offers language courses in English, Spanish, German, and Chinese, encouraging users to translate various documents while progressing through lessons Duolingo aims to address vocabulary challenges and improve language skills; however, its potential for vocabulary enhancement remains underutilized in Vietnamese educational contexts This gap in vocabulary teaching motivates the need for further exploration and implementation of Duolingo in Vietnam.

To improve the quality of English as a Foreign Language (EFL) teaching and learning in Vietnam, integrating Information and Communication Technology (ICT) in education is essential, providing valuable support for both teachers and students This study utilizes the Technology Acceptance Model (TAM), introduced by Fred Davis in 1989, which is widely recognized in the fields of information systems and technology research TAM aims to deepen the understanding of user acceptance processes and offers a theoretical basis for user testing methodologies It serves as a framework for modeling how users accept and utilize technology However, as noted by Legris, Ingham, and Collerette (2003), while TAM is a beneficial model, it should be incorporated into a broader framework that addresses human and social change processes as well as the adoption of innovation.

The Technology Acceptance Model (TAM) highlights two key factors that shape users' attitudes and intentions towards technology adoption: perceived usefulness (PU) and perceived ease of use (PEOU) Perceived usefulness is the belief that a system can improve job performance and efficiency, while perceived ease of use pertains to the expectation that a system will be effortless and user-friendly.

The Technology Acceptance Model (TAM) suggests that user-friendly technologies that require minimal effort are more likely to be adopted, especially in the context of language learning apps like Duolingo According to TAM, an individual's attitude towards technology adoption is influenced by perceived utility and ease of use, shaping their intention to embrace it When users find a technology beneficial and straightforward, they are more inclined to adopt it Researchers frequently utilize surveys and questionnaires based on TAM to evaluate a technology's perceived utility, ease of use, and users' attitudes and intentions, making it a valuable framework for understanding technology acceptance across various platforms.

This research focuses on the Technology Acceptance Model (TAM) to evaluate how Duolingo aids in vocabulary enhancement and its user-friendliness for students The study aims to determine if students perceive Duolingo as beneficial for vocabulary learning and whether its interface and exercises are intuitive for English as a Foreign Language (EFL) learners Additionally, the perceived usefulness (PU) and perceived ease of use (PEOU) of Duolingo influence students' behavioral intention (BI) and actual usage (AU), indicating their current engagement with the platform and their future intentions to utilize it for vocabulary acquisition.

The research explored the perceived usefulness and ease of use of Duolingo, emphasizing the role of student motivation and learning autonomy outside the classroom Grounded in Self-Determination Theory (SDT), developed by Ryan, Kuhl, and Deci in 1997, the study highlights how intrinsic motivation is driven by autonomy, competence, and relatedness SDT provides insights into fostering motivation by identifying environments that may hinder positive learning outcomes In this context, Duolingo's design allows learners to choose topics and control their learning pace, potentially enhancing their intrinsic motivation and autonomy in vocabulary acquisition Additionally, the study references Second Language Acquisition Theory (SLA) proposed by Stephen Krashen, further enriching the understanding of language learning dynamics.

In 1982, a comprehensive model emerged that significantly enhances our understanding of Second Language Acquisition (SLA), aiming to describe and explain the intricate process of acquiring a second language (L2) This model identifies both external and internal factors influencing why learners approach L2 acquisition in diverse ways It encompasses five key hypotheses: the Acquisition-Learning Hypothesis, the Monitor Hypothesis, the Natural Order Hypothesis, the Input Hypothesis, and the Affective Filter Hypothesis, each playing a vital role in elucidating the language acquisition journey.

Krashen's Input Hypothesis is pivotal in Second Language Acquisition (SLA), positing that learners acquire language most effectively through "comprehensible input" that slightly exceeds their current proficiency level This approach emphasizes the necessity for language input to be both understandable and challenging, promoting continuous skill development through meaningful engagement rather than isolated grammar drills This framework can be applied to investigate Duolingo's effectiveness in delivering vocabulary to English as a Foreign Language (EFL) students The study will assess how Duolingo provides comprehensible input, specifically focusing on students' perceptions of the platform's content and its impact on vocabulary acquisition, utilizing the Technology Acceptance Model (TAM) to evaluate perceived usefulness and ease of use.

4 input hypothesis could help to explain whether Duolingo had an impact on promoting students’ language acquisition.

Research aims 5 1.3

This research had two primary objectives: to examine the impact of Duolingo on vocabulary acquisition among high school students learning English as a foreign language (EFL), and to explore EFL students' perceptions regarding the use of the Duolingo app in their language learning process.

The research attempts to answer the following research questions:

1 To what extent does Duolingo application affect EFL students' vocabulary learning?

2 What are EFL students’ perceptions towards the benefits and challenges of the Duolingo application?

This study explored the impact of Duolingo on English vocabulary acquisition among EFL high school students, highlighting their perceptions of the platform It identified both the benefits and challenges faced by students while using Duolingo for English learning Additionally, the research presented opportunities for EFL students and teachers to utilize this innovative online tool to enhance vocabulary sources during the learning process, enabling educators to discover new applications that can effectively support their English teaching efforts.

This study serves as a valuable reference for researchers exploring English app implementation, enhancing the understanding of English teaching and learning It contributes to the literature on vocabulary acquisition within the Vietnamese educational context and aids educators and researchers in comprehending learners' vocabulary development Additionally, it highlights the role of advanced educational technology, empowering teachers to make informed pedagogical decisions in their careers.

The study highlighted the importance of implementing English apps to enhance language learning, thereby increasing students' awareness and providing them with more effective learning options Furthermore, it aims to alleviate the challenges posed by a dense school curriculum while improving vocabulary teaching and learning.

The present thesis is composed of five chapters: (1) Introduction, (2) Literature

Review, (3) Research Methodology, (4) Research Findings, (5) Discussion and Conclusions They are presented as follows:

Chapter One states the rationale for the study, research aims, research questions, significance of the study, and organization of the study.

Chapter Two explores the literature pertinent to the study, defining essential terms such as vocabulary and vocabulary learning It highlights the significance of vocabulary in education, the role of technology in language acquisition, and the current state of vocabulary learning among Vietnamese learners Additionally, the chapter discusses the Duolingo app, its features, and reviews related studies that investigate the effectiveness of vocabulary learning through the implementation of the Duolingo app.

Chapter Three describes the research methodology used in this study It comprises the design, participants, instruments, data collection procedures, and data analysis procedures.

Chapter Four presents the study's findings, focusing on EFL high school students' vocabulary acquisition through the implementation of the Duolingo app and their perceptions regarding its effectiveness.

Chapter Five provides a concise overview of the study's findings and engages in a thorough discussion to address the two research questions The chapter concludes by outlining the pedagogical implications, acknowledging the study's limitations, and offering suggestions for future research.

LITERATURE REVIEW 7 2.1 Vocabulary .7 2.1.1 Definition 7 2.1.2 Types of vocabulary .7 2.1.3 The importance

Participants 26 1

3.2.1 Participants for the experimental research approach

The study involved 80 EFL grade-10 students from a high school in the Mekong Delta, ultimately selecting 48 participants after evaluating their English proficiency through an entrance exam and mid-term test in Maths, Literature, and English This selection process ensured a consistent level of English competence among the participants, enhancing the reliability of the research Choosing grade-10 students was strategic, as they had already undergone assessments to accurately gauge their English skills, allowing for a more precise selection Additionally, these students had ample time to engage with the research and work on their language improvement, making the study a valuable resource for enhancing their English proficiency for future examinations.

In a study involving two randomly selected classes, both the experimental and control groups comprised 24 students each Both groups utilized the same Ministry of Education and Training (MoET)-approved English grade-10 course book, "Global Success," and attended three English lessons weekly.

Of this sample, ten students (41,6%) were female, and 14 students (58,4%) were male in the control group In the experimental group, there were 11 female students (45,8%) and 13 male students (54,2%).

Eighteen participants were involved in the experimental group, with six selected for a piloted interview and the remaining participating in official interviews to share their individual experiences and perceptions of the Duolingo app The participants were divided into three groups, allowing them to discuss the benefits and challenges of the app's implementation openly According to Rabiee (2004), focus-group interviews are most effective with six to eight participants, as this size enables in-depth exploration of diverse perspectives (Krueger and Casey, 2000) The researcher employed random selection to ensure a varied representation of opinions.

26 ensured objectivity and reduced mistakes in selection Moreover, the researcher could collect more insightful opinions from the interviewees.

Instruments 27 1

The current study aimed to evaluate high school students' English vocabulary learning by conducting two tests: a pretest before using Duolingo and a posttest afterward According to Djiwandono (2011), tests are essential tools for assessing an individual's knowledge and performance in specific areas This research utilized a two-group pretest and posttest experimental design, measuring the same dependent variable in both control and experimental groups (McCaleb, Anderson, and Hueston, 2008) The results from these assessments provided insights into the effectiveness of Duolingo in enhancing students' vocabulary skills.

Research by Nation (2001) indicates that learners can effectively remember words after they have been repeated or recycled at least seven times Duolingo applies this concept by consistently presenting vocabulary through diverse methods, including matching words with images, selecting meanings in Vietnamese or English, and engaging in listening exercises This multifaceted approach not only aids users in acquiring new vocabulary but also improves long-term retention To evaluate the effectiveness of this method, a pretest and posttest were administered over an 8-week period.

This study utilized the Updated Vocabulary Levels Test (Webb, Sasao & Ballance, 2017) to assess students' vocabulary knowledge across five levels, ranging from 1000 to 5000 words, with test items sourced from Nation’s (2012) BNC/COCA word lists Previous research indicated that this test effectively measures EFL learners' understanding of high-frequency words (Sun & Dang, 2020) The updated VLT, a widely recognized tool for evaluating L2 lexical knowledge since its original development by Nation (1983), allows participants to complete various levels based on their proficiency and the study's objectives It also enables learners to assess their vocabulary skills and identify improvement areas post-assessment Furthermore, the updated version enhances validity by incorporating items from a prestigious universal word list, while Duolingo's vocabulary resources align with the test items, making the updated VLT an appropriate choice for evaluating students' vocabulary sources following Duolingo app usage.

The current study adapted the updated Vocabulary Level Test (VLT) by Webb et al (2017) to suit its specific needs and context In this revised test, participants read meanings and selected appropriate words from a box across three word levels, focusing on the B1 target level for Vietnamese high school students, equivalent to the 3000 word level By excluding the 4000 and 5000 word levels, the adaptation aimed to alleviate pressure on participants The test design included more words than definitions, requiring participants to thoughtfully choose the correct matches, thereby minimizing random selections and peer copying, which could skew results Additionally, the written format of the test fostered logical thinking among participants.

At the start of the research, participants underwent a vocabulary test to assess their English proficiency prior to using the Duolingo app The test featured consistent content organized into four distinct codes to maintain accuracy Participants had a total of 90 minutes to complete the assessment.

After eight weeks of utilizing the Duolingo app, participants took a posttest to assess their English vocabulary proficiency This test mirrored the pretest in content but was divided into four distinct codes to maintain accuracy Participants were allotted 90 minutes to complete the assessment.

Focus-group interviews were conducted with three groups of six students each from the experimental group who completed both pretests and posttests This research aimed to explore EFL students' perceptions of Duolingo, highlighting its benefits and challenges The interview questions were developed based on the frameworks of Jaelani and Sutari (2021) and Muddin (2018), with modifications and additional questions introduced to better address the specific research question due to variations in participant situations.

Data collection 28 1

This study employed pretest-posttest designs as the primary method of data collection, a form of paired data analysis according to Bonate (2000) This design aimed

This experimental study aimed to evaluate the effectiveness of Duolingo by comparing test results from an experimental group before and after its use, while also analyzing the differences between control and experimental groups.

In a study comparing a control group and an experimental group, both groups received identical lessons from the same teacher and utilized similar classroom resources Participants completed a pretest prior to the intervention and a posttest afterward While the control group did not use any educational apps for English learning outside the classroom, the experimental group was instructed to use the Duolingo app This setup allowed the study to effectively measure the enhancement of vocabulary among EFL students utilizing the Duolingo app.

Before the main study, a vocabulary test was piloted to assess its timing and effectiveness The pilot involved 20 EFL students in the 10th grade, all of whom had not previously used Duolingo, as confirmed by a brief survey.

The participants, who were not part of the actual study but had equivalent English proficiency, received test instructions in both English and Vietnamese for clarity Following a pilot test of the vocabulary, the researcher collaborated with the supervisor to refine the vocabulary test before its official implementation Additionally, the test duration was extended to provide participants ample time to complete it.

A pretest was conducted to evaluate the current proficiency levels of 10th-grade participants who had not previously used Duolingo This assessment required participants to match words with their definitions by writing the words next to the corresponding definitions The pretest was completed within a 90-minute timeframe, and the results were later compared to those of a posttest.

Participants were introduced to Duolingo, a language-learning platform that offers various functionalities for learners, including topic-based skill development, daily speaking and listening practice, a study corner for revising mistakes and vocabulary, and engaging stories The app includes a mission and badge system to track daily progress and reward users for completing tasks To monitor the participants' progress, the teacher created a Zalo group where students were required to upload their weekly Duolingo results, ensuring consistent engagement with the app without direct reminders.

The experimental phase lasted eight weeks, culminating in a posttest for both groups to gather post-intervention data The posttest was designed to closely resemble the pretest, allowing for a straightforward comparison of results Furthermore, 18 participants from the experimental group at a high school in Can Tho City were selected for focus-group interviews during the study.

3.4.2.1 Rationale for using focus-group interviews

An interview is a dynamic interaction in which a researcher asks relevant questions to gather detailed information for their study This method is particularly advantageous in qualitative research, as it allows researchers to evaluate participants' behaviors, emotions, interests, and beliefs, while also exploring the deeper motivations behind specific events.

A focus-group interview is a widely used method that involves interviewing a group of individuals simultaneously to gather insights into their behaviors and opinions According to Folch-Lyin and Trost (1981), this approach aims to elucidate the reasons behind people's actions Unlike traditional interviews, focus-group interviews prioritize collecting participants' views without delving into the strengths and weaknesses of their responses The unique advantage of focus groups lies in their ability to generate data through the dynamic interaction among group members, as noted by Green et al (2003) Consequently, it is essential for participants to engage in open conversation and feel comfortable with one another during the discussion.

The focus-group interview method was selected for this study due to its flexibility in adapting questions and fostering dynamic group interactions, which enhance data collection This approach enables researchers to shape responses based on participants' opinions, facilitating the gathering of specific information efficiently It is particularly beneficial for examining hypotheses, as focus group moderators encourage participant interaction and observe group dynamics to uncover authentic attitudes and perspectives Moreover, the interview format helps create a comfortable environment for participants, promoting active engagement and idea sharing Thus, the focus-group interview is well-suited for the objectives of this study.

The interview questions were designed based on the literature review and categorized into two themes: benefits and challenges.

Before the study began, the researcher and colleagues evaluated the interview questions during the initial week A pilot test with six students, who were part of the study sample, was conducted to ensure effective communication in Vietnamese and assess their understanding of the questions This pilot phase allowed the researcher to refine the questions, duration, and order based on participant feedback Misunderstood questions were revised for clarity, and the feedback indicated that most questions were comprehensible and suitable for the actual interviews Additionally, the pilot interviews helped the researcher enhance their skills in conducting in-depth interviews The insights gained from these pilot sessions led to important adjustments in question clarity, interview duration, and content sequence in preparation for the main study (Nguyen, 2014).

A series of focus-group interviews was conducted with 18 participants, divided into three groups, each lasting 10 to 15 minutes during breaks or after school The interviews were recorded, transcribed, and translated into English for data analysis Participants were informed about the study's objectives and the significance of their involvement prior to the interviews, which were held in Vietnamese and began with open-ended questions, followed by probes for clarification.

Table 3.1 Summary of research instruments

The study aims to gather data on students' vocabulary sources before and after utilizing the Duolingo app, focusing on their perceptions of the advantages and challenges associated with its implementation By analyzing these insights, the research seeks to understand the effectiveness of Duolingo in enhancing vocabulary acquisition among students.

Elicitation formatVocabulary Level Test Twelve questions, including two themes

Procedure .32 3.6 Data

The data were collected in 15 weeks in the second semester of the academic school year 2023-2024 (as outlined in Table 3.2)

Table 3.2 An overview of data collection procedures

Week 1Constructing the pretest of vocabulary

Delivering the pretest to the participants Introducing Duolingo

Week 3Analyzing data from the pretest

Week 4-5Following participants in using Duolingo

Week 7Piloting the interview questions

Week 8Adjusting the interview questions

Week 11Analyzing data from the posttest and interviewsWeek

Week 13 -14Writing the draft and completing the thesis

The data collected from pretests and posttests were analyzed using SPSS software version 20.0 A Paired Samples T-test was conducted to determine if there was a significant difference between the pre-test and post-test results for each word level in both the control and experimental groups Additionally, an Independent Samples T-test was performed to compare the mean scores of pretests and posttests across both groups The findings indicated a notable difference in participants' learning progress over the 8-week intervention period.

This research utilized Thematic Analysis, as outlined by Braun and Clarke (2012), to analyze data gathered from interviews Thematic analysis is a widely used method in qualitative research that focuses on identifying, analyzing, and interpreting patterns and themes within qualitative data The process involves six distinct steps to ensure a comprehensive understanding of the data.

1 Becoming familiar with the data

The interviews were analyzed using Thematic Analysis, beginning with multiple listenings of the recordings to create precise transcriptions The researcher meticulously reviewed these transcripts alongside session notes, identifying key statements that provided valuable insights into participants' views on Duolingo Subsequently, the data from the respondents' answers was systematically coded for further analysis.

The analysis utilized Boyatzis's (1988) framework to identify themes from the interview process, highlighting both similarities and differences in participants' responses Each theme was supported by direct quotes from the participants, ensuring a robust interpretation of the data To enhance dependability, the researcher translated Vietnamese responses into English and sent them to participants for verification, confirming the accuracy of the translations Furthermore, the supervisor reviewed the interview transcripts to ensure clarity and the accurate conveyance of intended meanings.

According to Woodrow (2014), validity pertains to the accuracy and truthfulness of a measurement It addressed whether a test or instrument actually measures what it

The study aimed to assess the validity of the Vocabulary Test by evaluating a group of students with similar proficiency levels and conditions The test was adapted from a standard format to align with the capabilities of the participants, using a pilot group for refinement This approach ensured the effectiveness of measuring students' vocabulary competence.

The importance of ethical considerations in social research, especially in educational studies involving students, has grown significantly Key aspects such as informed consent, securing study permissions, maintaining participant anonymity, and addressing potential inequalities are carefully integrated into the study's methodological design.

This chapter presents the findings of the study, which employed an experimental research design to compare a control group and an experimental group over eight weeks Additionally, qualitative data from focus group interviews were analyzed to gain a deeper understanding of EFL high school students' perceptions regarding the implementation of the Duolingo app.

The effect of Duolingo application on EFL high school students’ vocabulary

This study aimed to evaluate the impact of the Duolingo app on vocabulary learning among 48 high school EFL students, who were divided into a control group and an experimental group Both groups completed a pretest, after which the experimental group utilized Duolingo for eight weeks Following this period, a posttest was administered to assess the vocabulary improvement in both groups Data analysis was conducted using SPSS version 20.0, employing Paired Samples T-tests and Independent Samples T-tests to compare vocabulary learning outcomes Results were categorized into different word levels: PRE1 and POST1 for the 1000 Word Level, PRE2 and POST2 for the 2000 Word Level, and PRE3 and POST3 for the 3000 Word Level, with findings summarized in accompanying tables.

Webb et al emphasize the importance of analyzing individual level scores rather than focusing solely on total scores across all levels In the revised versions of the Vocabulary Level Test (VLT), it is recommended that mastery scores for the 1000, 2000, and 3000 levels should reach a benchmark of 29 out of 30 (Webb, Sasao & Balance, 2017).

The current study focuses on grade-10 EFL students, aiming to achieve a target vocabulary level of 3, which corresponds to CEFR Level B1 This level indicates that students should be able to master approximately 2,000 words, as outlined by Nation and Crabbe (1991) and detailed in CEFR standards by the Council of Europe (2001) and Hoang (2022).

The analysis of the results concentrated on the top three Word Levels from a set of 3000 high-frequency words, even though participants were assessed across five Word Levels As shown in Table 4.1, the number of participants who mastered the 1000, 2000, and 3000 Word Levels was documented according to the established standards.

35 Table 4.1 The number of participants mastering at each word level.

A Paired Samples T-test was conducted to evaluate the differences in vocabulary learning scores among EFL high school students before and after utilizing the Duolingo app, comparing both the control and experimental groups The findings are detailed in Tables 4.2 and 4.3.

4.1.1 Participants’ vocabulary learning in the pretest and the posttest between a control group and an experimental group

EFL students in both groups demonstrated significantly higher mean scores following the treatment, indicating improved vocabulary mastery To evaluate the differences between the two groups, an Independent Samples t-Test was performed, focusing on EFL high students' vocabulary proficiency at the 1000, 2000, and 3000 Word Levels The findings are detailed in Tables 4.2, 4.3, and 4.4.

Before the treatment, the mean score at the 1000 Word Level for the experimental group (M = 1000.08; SD = 3.833) was comparable to that of the control group (M = 1000.83; SD = 4.659), with no significant difference observed (t = -2.639, p = 0.99 > 0.05) This indicates that the pretest results for the 1000 Word Level were equivalent between both groups in the study.

The study found no significant difference in vocabulary learning between the experimental group (M = 0.05, SD = 1.532) and the control group (M' = 0.42, SD = 2.842) after treatment (t = -1.644, p = 0.492) Both groups demonstrated equivalent proficiency at the 1000 Word Level However, posttest results revealed that a greater number of students in the experimental group (17 out of 24) achieved mastery of the 1000 Word Level compared to the control group (7 out of 24).

36 Table 4.2 The EFL high school students’ vocabulary learning at 1000 Word Level between the control group and the experimental group before and after the treatmentTest Group N Mean SDMean

Before the treatment, the mean vocabulary scores at the 2000 Word Level for the experimental group (M=79; SD=5.634) and the control group (M=21; SD=5.801) were comparable Statistical analysis revealed no significant difference between the two groups (t=-0.959, p=0.784 > 0.05), indicating that EFL high school students' vocabulary learning was similar in both groups prior to the intervention.

The analysis revealed no significant difference in vocabulary learning outcomes between the experimental group (M=##.04, SD=4.515) and the control group (M=##.46, SD=4.718), with a t-value of -0.438 and a p-value of 0.893, indicating equality in their performance at the 2000 Word Level Notably, only one student from each group achieved mastery of the 2000 Word Level, as the majority did not meet the standard benchmark, scoring 29 out of 30 items.

Table 4.3 The EFL high school students’ vocabulary learning at 2000 Word Level between the control group and the experimental group before and after the treatmentTest Group NMea nSDMean

The analysis of Table 4.4 reveals that the mean score of the experimental group (M=4.92; SD=3.729) was comparable to that of the control group (M=6.25; SD=6.243) at the 3000 Word Level prior to treatment Statistical comparison indicated no significant difference in mean scores between the two groups (t=0.898, p=0.109 > 0.05), demonstrating that EFL high school students' vocabulary learning was equivalent in both groups before the intervention at the 3000 Word Level.

The results indicate that there was no significant difference in vocabulary learning between the experimental group (M=33; SD=6.670) and the control group (M=9.17; SD=6.644) following the treatment, as evidenced by a t-value of -2.168 and a p-value of 0.5473, which is greater than the 0.05 significance level.

Both groups demonstrated equal performance at the 3000 Word Level, with no participants achieving mastery in this category Although individual posttest scores exceeded pretest scores, there was no overall improvement to the mastery level in either group (Appendix 3).

Table 4.4 The EFL high school students’ vocabulary learning at 3000 Word Level between the control group and the experimental group before and after the treatmentTest Group N

4.1.2 Participants’ vocabulary learning within the control group before and after the treatment

According to Table 4.5, a Paired Samples T-test was run to check the differences between the mean score of the pretest and that of the posttest at the 1000, 2000 and

The analysis of the control group's performance revealed significant improvements in the mean scores of EFL high school students at both the 1000 Word Level (Pretest: M=11.83, SD=4.659; Posttest: M=27.42, SD=2.842; p=0.00, t=-4.554) and the 2000 Word Level (Pretest: M=21, SD=5.801; Posttest: M=46, SD=4.718; p=0.00, t=-5.689) All significance values were below 0.05, indicating that the posttest scores for both word levels were significantly higher than the pretest scores This suggests that EFL learners in the control group made notable progress in their vocabulary acquisition, despite not receiving the same treatment as the experimental group.

The analysis of the mean scores at the 3000 Word Level revealed no significant difference between the pretest (M=6.25; SD=6.243) and posttest (M=9.17; SD=6.644) results, with a p-value of 0.131 and t-value of -1.564 Since the significance level was above 0.05, it can be concluded that EFL high school students did not show improvement in their vocabulary mastery after the study.

EFL high school students’ perceptions of Duolingo app implementation 41

4.2.1 Qualitative data about EFL high school students’ perceptions of the benefits of Duolingo app implementation

Firstly, regarding students' interest in using Duolingo, most of the participants showed their positive attitudes towards the Duolingo app In particular, they rated Duolingo highly, ranging from 8 to 10 marks.

However, there was a student rating Duolingo as less effective than other participants.

Participants agree that Duolingo is appropriate for all age groups, ranging from primary school students to university learners, making it a versatile language-learning tool suitable for most individuals.

It suits primary, secondary, and university schools.

However, some participants also mentioned that it could not be suitable for some students.

But some learners are not suitable, and other situations.

I agree with you It depends on the learners’ hobbies.

All participants reported enhancements in their English skills after using Duolingo, with individual experiences varying among them.

I think it is writing skills.

Because words are repeated, I get used to them, remember them, and write them easily.

I think it is Grammar Because it is repeated many times, I get used to making sentences with subjects and verbs and using tenses Therefore, I find Grammar good.

I think listening skills Because it includes slow and fast listening tasks depending on my level.

I think it provides me with vocabulary sources, and the second one is that I have a learning environment to listen to native speakers.

Speaking skills are essential because I can easily acquire and learn pronunciation.

Because language connects people together, I think the most improved skill is speaking to help me communicate with people.

Vocabulary and the ability to review lessons carefully before doing tests.

Because I can practice patience, it makes me more careful before making a decision.

It helps me improve my listening skills.

Because it helps me practice listening.

When I use Duolingo, I can read vocabulary and I can choose vocabulary to fill in.

I think I can improve my writing skills, grammar, and vocabulary.

Because it focuses on practicing vocabulary and grammar, it has gap-fill sentences in Duolingo.

Duolingo enhances listening skills through its engaging feature that includes stories and character conversations This allows users to listen to dialogues, practice correct pronunciations, and take listening tests to expand their vocabulary.

Vocabulary and listening skills are crucial for effective communication I share my friend's perspective on the importance of listening skills, while I find that the repetition of certain words during discussions aids in quick memorization of vocabulary.

They are vocabulary and speaking skills Because when I mispronounce words, Duolingo will correct them Moreover, I can enrich my vocabulary source. (Interview 3, lines 353-354)

Fourthly, the students said that Duolingo supported their learning in the classroom.

It helps me improve fundamental knowledge and memorize preceding lessons, such as grammar structures and vocabulary.

Duolingo enhances my classroom learning by providing advanced vocabulary that complements the limited words I can learn in class This tool allows me to supplement my knowledge with new words and deepen my understanding, making it an invaluable resource for my language development.

Pronunciation in Duolingo helps me with my tests relevant to pronunciation and stress sections in the classroom.

I think it helps me better my in-class tests High-level rounds in Duolingo have many grammar structures, which often appear in my tests in class (Interview

I think it helps me to review some grammar structures and vocabulary.

It creates my basic vocabulary, words to write, speak, and test.

I can gradually learn vocabulary because it has fundamental lessons to help me revise preceded words.

Duolingo reinforces my vocabulary by repeatedly introducing fundamental words that I struggle with, enhancing my memorization and language retention This consistent practice not only bolsters my vocabulary but also significantly improves my writing skills and understanding of grammar structures.

It is listening skills because I know how to pronounce the words For example, when teachers say a word in the classroom, I can recognize it (Interview 2, lines 233-234)

The structured learning pathway, progressing from simple to complex tasks, enhances my motivation to learn In Round 1, I was introduced to key vocabulary, while Round 2 reinforced my understanding by presenting relevant sentences that incorporated those words, aiding in long-term retention.

It teaches me how to speak and pronounce words more correctly

In some lessons, I think I use Duolingo on my phone, which helps me understand in-class lessons and learn more new words.

It has more new words, similar to in-class lessons, so that I can understand the lesson more effectively.

44 Furthermore, Duolingo was believed to help participants in their daily lives.

Sometimes, it gives me vocabulary about culture.

When we communicate with foreigners, most use cultural vocabulary I don’t know However, Duolingo provides me with cultural vocabulary when I use it, which is beneficial.

It is beneficial and good for me Because I can learn new words and learn how to communicate.

It teaches me how to speak and pronounce words more correctly

It helps me improve my listening skills.

I can hear and understand what foreigners say.

It helps me listen better.

It is communication skills because it is easy to communicate with my available vocabulary.

It is also communication skills because I needn’t think of grammar structures when talking.

It helps to improve my communication skills I can listen to native speakers and hear how they pronounce words correctly.

Both male and female voices are used in vocabulary and pronunciation It helps me practice listening skills with different accents when communicating with foreigners.

It also has intonation, which makes sentences different I can understand the speakers’ feelings if I can hear the intonation.

It helps me relax and feel happy to learn and play games in Duolingo.

4.2.2 Qualitative data about EFL high school students’ perceptions of the challenges of Duolingo app implementation

Participants encountered various challenges while using the Duolingo app, with the most common issue being the frequent presence of advertisements Many users expressed their frustration, stating, "It has advertisements," highlighting how this aspect affected their overall experience with the app.

The biggest challenge is advertisements.

One more challenge is that the appearance of advertisements distracts me from learning, and I have to pay money to block advertisements.

Participants also expressed their negative attitudes toward advertisements.

It interrupts my learning and distracts me from concentration, decreasing my acquisition.

It wastes my time, and I feel annoyed waiting for them.

The number of turns I can take tests each day is limited If I make mistakes, I will lose one turn, which I must watch advertisements to restore.

Because it advertises games, it distracts me from learning.

It costs money to upgrade the version to gain other interests.

Moreover, the Internet connection was also mentioned as another challenge during the Duolingo app implementation.

It depends on the Internet connection.

Duolingo depends too much on the Internet If there is no Internet connection, I cannot learn in Duolingo It prevents me from learning.

Another challenge is that I need an Internet connection to use Duolingo; otherwise, I cannot use it.

46 Finally, some students also mentioned other challenges They said that repeated questions made them bored.

It interrupts my learning and distracts me from concentration, decreasing my acquisition.

If I make many mistakes, I will lose all diamonds (a unit of award in Duolingo).

If I continue to learn, I will have to watch advertisements.

Too many repeated questions waste my time.

Moreover, the limit of turns the participants could play also prevented them from using the Duolingo app.

The number of turns I can take tests each day is limited If I make mistakes, I will lose one turn, which I must watch advertisements to restore.

Another participant also complained about the quality of the speaking system.

In speaking tasks, the system cannot record everything I say; I must repeat it many times Speaking in public places is also challenging because I have to speak loudly.

Focus-group interviews revealed that participants had a positive perception of the Duolingo app, recognizing it as a valuable tool for enhancing various English skills, including vocabulary, listening, speaking, writing, grammar, and pronunciation The app's integration of cultural and communicative vocabulary allowed users to practice English in real-life contexts, facilitating the application of their knowledge Supporting the findings from pretests and posttests, participants in the experimental group showed greater vocabulary improvement than those in the control group, with many mastering the 1000 Word Level This quantitative and qualitative evidence demonstrated Duolingo's positive impact on EFL high school students' vocabulary learning However, participants noted drawbacks, particularly the disruptive nature of advertisements and internet connectivity issues, which led to frustration and decreased motivation to use the app Additionally, excessive repetition was cited as a source of boredom and a perceived waste of time.

Participants faced challenges in the Duolingo app due to repetitive tasks and a low-quality recording system Despite providing correct answers, the system failed to accurately record their responses, resulting in incorrect markings This issue not only caused participants to lose their turns but also restricted their opportunities to effectively engage with the app.

DISCUSSIONS AND CONCLUSIONS

Summary of key findings 49 5.2

This study explored how high school students learning English as a Foreign Language (EFL) enhance their vocabulary through the Duolingo app, along with their perceptions regarding its use The key findings provide valuable insights into the effectiveness of the Duolingo app in vocabulary acquisition for EFL students and highlight their attitudes towards its implementation in their learning process.

The study examined the impact of the Duolingo application on EFL students' vocabulary acquisition Results from pretests and posttests revealed that both control and experimental groups showed vocabulary improvement Notably, students utilizing the Duolingo app demonstrated a stronger grasp of vocabulary at the 1000 Word Level compared to their peers who did not use the app However, neither group achieved mastery at the 2000 and 3000 Word Levels.

The study on EFL students' perceptions of the Duolingo application revealed both benefits and challenges associated with its use Participants reported positive views, noting that Duolingo is suitable for learners of all ages and enhances skills in listening, writing, speaking, and grammar Additionally, the app exposes students to cultural vocabulary and native accents, aiding real communication However, challenges emerged, including interruptions from advertisements and internet connectivity issues, which frustrated users Furthermore, excessive repetition and system faults were also identified as significant drawbacks.

5.2.1 The effect of Duolingo application on Vietnamese EFL high school students’ vocabulary learning

Learning a foreign language requires dedication from both learners and educators While there are numerous English skills to develop, time constraints and various factors can hinder comprehensive mastery Therefore, the focus of this research is on enhancing English vocabulary, which is essential for effective communication and language proficiency.

This study explored the effectiveness of the Duolingo app in enhancing vocabulary learning among 10th-grade students A total of 48 participants were divided into a control group and an experimental group, each consisting of 24 students The control group utilized traditional teaching methods with the Global Success textbook, while the experimental group supplemented their learning with the Duolingo app After an eight-week intervention, results indicated that while the mean scores of both groups were similar, the experimental group demonstrated a slight improvement, particularly at the 1000 Word Level, suggesting the potential benefits of integrating technology in language education.

The study revealed that the Duolingo app significantly enhances vocabulary learning among students, with noticeable improvements across all Word Levels In contrast, the control group only demonstrated minor advancements at the 1000 and 2000 word levels, as indicated by their posttest scores, while showing minimal progress at the 3000 Word Level Ultimately, the control group participants struggled to master new Word Levels, managing to retain vocabulary primarily at the CEFR Level A2.

The experimental group demonstrated significantly better results compared to the control group As shown in Tables 4.6, students utilizing the Duolingo app for eight weeks exhibited notable improvements in their posttest scores compared to their pretest scores at the 1000 and 2000 levels.

The study revealed that participants successfully mastered a significant amount of vocabulary at the 1000 Word Level, with most achieving proficiency in this area by the end of the study However, improvements at the 2000 and 3000 Word Levels were minimal, as indicated by the lack of significant score increases While the scores at the 1000 and 2000 Word Levels were notably high and above average, participants struggled to reach higher vocabulary levels post-treatment Overall, the experimental group demonstrated a greater mastery of words in the posttest, particularly at the 1000 Word Level.

The posttest results indicated that while the 3000 Word Level was higher, it remained below average This finding aligns with Vu and Nguyen's (2019) study, which revealed that only a limited number of 12th-grade students had mastered the 2000 Word Level, with even fewer achieving proficiency at the 3000 Word Level Despite this, the Duolingo app demonstrated effectiveness in enhancing students' vocabulary acquisition, suggesting its positive impact on learning English vocabulary.

The experimental group demonstrated significant improvement in vocabulary learning following the intervention, corroborating findings from previous research Notably, Wijaya, Yufrizal, and Kadaryanto (2016) reported enhanced student outcomes through the use of Duolingo, while Muddin (2018) also found that the average posttest scores were notably higher.

Research indicates that using the Duolingo app significantly enhances vocabulary learning among EFL high school students, as evidenced by an average pretest score improvement of 50 points Thus, it can be concluded that Duolingo has a positive impact on students' English vocabulary acquisition.

More than half of the students in the experimental group achieved mastery of the 1000 Word Level, but struggled with the 2000 and 3000 Word Levels This finding is consistent with previous research from Denmark, Spain, and Taiwan, which indicated that many learners had not mastered the most frequent 2000 words, and a significant number had not even mastered the 1000 words In contrast, Nguyen's study found that Vietnamese EFL high school students could master the 2000 most frequent words but not the 3000 Additionally, Muddin's research suggested that Duolingo is effective for beginners, while Garcia noted its limitations at higher levels due to its Direct-Translation Method Consequently, this study demonstrates that the Duolingo app aids EFL high school students in vocabulary acquisition, particularly at the 1000 Word Level Given that the Ministry of Education and Training (MoET) targets a B1 VSTEP level for high school students, it is understandable that tenth graders did not master the 3000 Word Level.

In summary, the Duolingo app significantly enhances students' vocabulary acquisition, particularly at the 1000-word level While mastery at higher frequency word levels was not achieved in this study, students demonstrated notable improvements in their vocabulary skills after utilizing the app This tool offers valuable support for EFL learners, facilitating their journey in English language learning.

5.2.2 EFL high school Vietnamese students’ perception of Duolingo app implementation

The research interviews revealed that students had a positive perception of the Duolingo app, despite facing some challenges Participants recognized multiple benefits of the app and expressed their intention to continue using it after eight weeks, believing it to be suitable for all ages These findings align with previous studies by Tiara et al (2021), Nasrul and Fatimah (2023), Muddin (2018), and Wijaya et al (2016), which highlighted Duolingo's appeal to learners ranging from beginners to high school students Consequently, the research suggests that Duolingo can effectively broaden its user base among those looking to enhance their English language skills.

The findings of the interviews also indicated that EFL high school students appreciated the benefits of the Duolingo app for their listening skills The participants

A recent study revealed that 51 participants enhanced at least one English skill after utilizing the Duolingo app, demonstrating improvements in listening, reading, writing, speaking, vocabulary, pronunciation, and grammar This indicates that the Duolingo app is equipped with diverse exercises tailored to meet the needs of various learners These findings align with previous research in the field (e.g., Muddin, 2018; Nguyen and Thai, 2024; Jaelani and Sutari).

Conclusion .54 5.4 Implications

Research highlights Duolingo's effectiveness in enhancing vocabulary acquisition among EFL high school students in Vietnam The findings suggest that Duolingo is a highly effective tool for early-stage vocabulary learning, as it allows students to reinforce their knowledge through repeated exposure to words in various contexts, promoting deeper memorization and retention.

Students find Duolingo engaging and user-friendly, making it an effective tool for learning English anytime and anywhere Its accessibility allows for easy comprehension and improvement of English skills, while the platform's interactive features keep learners motivated and active in their studies Utilizing the app at home further enhances their understanding of the material.

Students have reported significant satisfaction with Duolingo's features, noting their positive impact on vocabulary and grammar development, as well as overall motivation and engagement in language learning However, there are areas for improvement, specifically concerning the presence of advertisements and the requirement for a stable internet connection.

This research reveals valuable insights into EFL high school students' vocabulary learning and their perceptions of the Duolingo app's implementation The findings highlight the effectiveness of the app in enhancing vocabulary acquisition, suggesting that educators consider integrating digital tools like Duolingo into their teaching strategies to improve student engagement and learning outcomes.

Integrating Duolingo mobile applications into language learning curricula can greatly improve EFL students' vocabulary acquisition By utilizing these apps, educators can incorporate authentic materials and offer a variety of learning tools, fostering a more immersive and engaging educational experience Research underscores the advantages of personalized learning pathways and real-time feedback, further enhancing the effectiveness of language instruction.

Incorporating 54 interaction features and gratification elements significantly enhances user engagement and motivation, providing valuable insights for developing effective language learning practices tailored to the diverse needs and preferences of EFL students.

The study revealed that students have a positive perception of the Duolingo app, viewing it as an effective and user-friendly educational tool Consequently, educators should facilitate opportunities for lesson reviews and inspire students to take an active, motivated, and responsible approach to their learning.

Limitations

The current study successfully met its objectives; however, it faced two significant limitations Firstly, the sample size was limited, consisting of only 48 participants evenly split between the control and experimental groups, primarily sourced from a specific province in the Mekong Delta Consequently, the results may not be applicable to all English as a Foreign Language (EFL) students across Vietnam.

The limited time allocated for English study in state schools, with only three periods per week, hindered students' ability to focus on their language practice and the use of Duolingo The eight-week experimental duration was insufficient for participants to prioritize their English studies or gain substantial vocabulary exposure With more time and fewer distractions from other subjects, students might have achieved better results on the posttest, suggesting that the short duration did not allow for consistent and sustained improvement in their English skills.

Future studies should expand their research to include a larger population of EFL students across diverse contexts to gain a more comprehensive understanding of the issue being investigated.

A comprehensive study should be conducted to assess the effectiveness of the Duolingo app across all English language skills, determining its overall impact on language learning.

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The Vocabulary Test is designed to assess your understanding of words and their meanings You will have 90 minutes to complete the test, which consists of reading definitions and writing the corresponding words from a provided box You must complete this task within 30 minutes For example, you may be asked to identify words related to categories such as game, island, mouth, movie, song, and yard.

1 land with water all around itisland2 part of your body used for eating and talkingmouth3 piece of musicsong

PART 1 boy rent report size station thing

1 how big or small something is

2 place buses and trains go to

_ ear gold lake letter office people

_ fellow hat ice joke light system

9 something worn on your head

_ date forest mistake new record shop

12 something that is not right

_ bar conversation neighbor rain rubbish shirt

14 things that are thrown away

_ continue cook pull sail share

16 hold and move something toward yourself _

_ enter finish happen own sing worry

21 have something that is yours

65 arrive collect consider glance need pack

23 reach the place you are going

_ affordable beautiful boring dry rough tall

_ closed dirty empty musical orange sad

PART 2 capital career committee exam fence option

_ guard lesson library license monkey soup

4 food made with lots of water

5 person who watches for danger

6 place where many books are kept _ brake crown hero language mission tale

7 hat worn by a king or queen

_ affair carrot damage desert shelter thief

_ advice hobby industry soil steak storm

15 things that you often enjoy doing _ burst cheat direct operate presume wander