Two hundred people who live in San Francisco volunteered to participate in a statistical study. The volunteers were divided into two groups by age, with people under 40 years old in group 1 and people 40 years of age and older in group 2. Those in group 1 were asked to go in for sports once a day for 1 month. Those in group 2 were asked not to go in for sports for 1 month. At the end of the month, progress in weight reduction was significantly higher for group 1 than for group 2. From the resulting data, the researchers concluded that daily sports exercises help every San Francisco resident lose weight faster. Based on the study design, do you think that the conclusions are reasonable?
A)The conclusions are reasonable because this was an experiment.
B)The conclusions are not reasonable because this was not an experiment with random assignment of subjects to experimental groups.
C)The conclusions are not reasonable because this was an observational study.
D)The conclusions are reasonable because this was an experiment with random assignment of subjects to experimental groups.
E)The conclusions are not reasonable because only volunteers participated in the study.

Question

Quizplus · Accepted Answer

The conclusions are not reasonable because the study did not use random assignment, which is necessary to establish causation. The groups were divided by age, which could introduce confounding variables.

Two Hundred People Who Live in San Francisco Volunteered to Participate