A researcher wants to know how often adults in a city exercise. She surveys only people leaving a gym. What is the main concern with this…

A good sample must represent the whole population. People leaving a gym are more likely to exercise regularly than adults in general, so surveying only them over-represents exercisers and will overestimate how often adults exercise. The main concern is bias, choice B. Choice A is not the main issue, since the problem says nothing about the size, and a large biased sample would be just as misleading. Choice C is not supported, since nothing is said about the wording of the questions. Choice D is wrong because the sampling method itself distorts the result. A random sample of all adults in the city would fix the problem.