A physician is studying the effects of a new exercise program on weight loss. 130 volunteers participate in the study, half of which are asked to follow the new exercise program and half of which are asked to follow an existing exercise program. After 60 days, weight loss is measured. (a) Is this study an experiment or an observational study?

a. Observational study

b. Experiment

c. There is not enough information to tell

(b) The physician suspects that the exercise program may affect men differently from women. What is the best way to modify the study to account for this?

a. Have all the men in the study follow the new exercise program and all the women in the study follow the existing exercise program.

b. Have the men in the study follow their exercise program for 30 days and the women in the study follow their exercise program for 60 days.

c. Before randomly assigning participants to each exercise program, block based on gender.

(c) What is the purpose of having half of the volunteers follow an existing exercise program?

a. The physician needs to be able to compare the weight loss of people following the new exercise program to something. Having a control group allows them to do this

b. People who volunteer for this study are likely trying to lose weight, so they might lose weight for reasons unrelated to their exercise program (for instance, if they also follow some diet). Having a control group takes this into account.

c. Both of the above are good reasons to have half of the volunteers follow an existing exercise program.

(d) If the study were modified to include 260 participants instead of 130 participants, what effect would this have on bias and variability?

a. Bias would be decreased.

b. Variability would be decreased.

c. Both bias and variability would be decreased.

d. Increasing the sample size will not affect bias or variability.