In the experiment of the preceding exercise, the subjects were randomly assigned to the different treatments. What is the most important reason for this random assignment?

a. Random assignment eliminates the effects of other variables such as stress and body weight.

b. Random assignment is a good way to create groups of subjects that are roughly equivalent at the beginning of the experiment.

c. Random assignment makes it possible to make a conclusion about all men.

d. Random assignment reduces the amount of variation in blood pressure.

e. Random assignment prevents the placebo effect from ruining the results of the study.