Lecture Marketing research (12th edition) - Chapter 15: Sample size and statistical theory

Chapter 15 - Sample size and statistical theory. In this chapter, the following content will be discussed: Determining the sample size, factors determining sample size, population characteristics/parameters, sample characteristics/statistics,...

• Number of groups and subgroups within the  sample

• Measure of population dispersion

• Based on degree to which a response differs from population  average response

• The difference of each value from its mean is squared and averaged  across all responses

• Sample mean (    ) is used to estimate the unknown population mean

Example: A sample of symphony season­ticket holders

X

Sample mean

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standard error of      decreases as the sample size gets  larger

The effect of increasing sample size on the normal distribution of X

necessary to estimate it with the sample standard  deviation

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X

X

X

Size of Interval Estimate depends on:

• Confidence level

• Population standard deviation Sample size

Options:

• Use a sample standard deviation obtained from a  previous comparable survey or from a pilot 

survey

• Estimate the sample standard deviation (s) 

subjectively

Population variance,

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Sample Size Formulas

• Researcher may require the sample estimate 

be within plus or minus G percentage points of  the population value

where

Marketing Research 12th Edition

End of Chapter Fifteen