A Physical Education Researcher Wishes to Determine If Walking Every

Multiple Choice

A physical education researcher wishes to determine if walking every day affects the health of middle-aged men. The researcher randomly identifies 400 participants in two groups. Members of one group belong to a health club and walk on its track and members of the other do not. After two months, the researcher decides the group who walks daily is healthier and concludes that walking positively affects men's health. This conclusion is of questionable validity because:

A) of the placebo effect.
B) of confounding variables in the study.
C) the study is not double-blind.
D) the researcher is not a doctor.