Question

A weight-loss guru is offering free exercise training and diet plans for people who want to participate in her program. She finds that 85 percent of the participants who signed up lost an average of 30 pounds in just six months. She then promotes her program as the most effective plan available, and promises each participant a weight loss of 20 pounds or more. Is her plan really as effective as she says?

Answer 1

Answer:

No; the study is based on a volunteer sample, which may be very different from a randomly selected one.

Explanation

Her plan cannot be effective because she could base her own judgenent on samples that was randomly selected for consideration.