Which conclusion is best supported by this study?

Question

A gym posted a link to a survey on its website. Members chose whether to respond. Among the members who did respond, those who had attended a new fitness class reported higher energy levels than those who had not.

Accepted Answer

A. Among the members who responded, attending the class is associated with reporting higher energy levels.. Members chose whether to respond and chose whether to attend the class, so there was neither random selection nor random assignment. That limits the finding to an association, and only among the people who actually responded.

Answer

B. Attending the class causes gym members to have higher energy levels. — Nobody was assigned to attend. Members who already felt energetic are more likely to have signed up for a new class, which would produce this pattern with no effect from the class at all.

Answer

C. The result can be generalised to all members of the gym. — Members opted in to the survey rather than being chosen at random, so respondents are probably the more enthusiastic ones and don't represent the membership.

Answer

D. The result can be generalised to all adults who exercise regularly. — This over-reaches twice: beyond the self-selected respondents, and beyond this gym to exercising adults generally.

Problem-Solving and Data Analysis practice question

Answer: A. Among the members who responded, attending the class is associated with reporting higher energy levels.

Why the other answers are wrong

More Problem-Solving and Data Analysis questions