Problem-Solving and Data AnalysisHardWhich sample gives the most reliable estimate
Problem-Solving and Data Analysis practice question
A researcher wants to estimate the mean commute time of all employees at a large company. Four sampling plans are proposed. Which plan is most likely to produce an estimate with the smallest margin of error and no selection bias?
- A. Randomly select 400 employees from the full staff list.Correct
- B. Randomly select 50 employees from the full staff list.
- C. Survey the 400 employees who arrive earliest on Monday.
- D. Survey 400 employees who volunteer by replying to an email.
Answer: A. Randomly select 400 employees from the full staff list.
Random selection avoids bias, and a larger sample gives a smaller margin of error: 400 random employees.
Why the other answers are wrong
- B. Randomly select 50 employees from the full staff list.
- Random but small; 50 gives a larger margin of error than 400.
- C. Survey the 400 employees who arrive earliest on Monday.
- Early arrivers may have unusual commutes — a biased sample.
- D. Survey 400 employees who volunteer by replying to an email.
- Volunteers self-select, which introduces bias.
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