A journalist surveys people leaving a gym about their weekly exercise habits. Which of the following best explains why this sample is likely to be biased?

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Question

A journalist surveys people leaving a gym about their weekly exercise habits. Which of the following best explains why this sample is likely to be biased?

Accepted Answer

B: People at a gym are likely to exercise more than the general population — Sampling only gym users introduces bias because this group is self-selected and likely to be more active than the general population, so the results will not be representative. This is an example of opportunity sampling producing a biased sample due to where and whom you choose to survey. Sample size (A) and survey method (C) are separate issues.

Answer

C: The journalist should have used a questionnaire instead

Answer

D: Gyms attract people from different age groups, skewing the data

Answer

A: The sample size is probably too small to be valid

Answer

B: People at a gym are likely to exercise more than the general population

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