Cocaine addicts need cocaine to feel any pleasure, so perhaps giving them an antidepressant drug will help. A 3-year study with 72 chronic cocaine users compared an antidepressant drug called desipramine with lithium (a standard drug to treat cocaine addiction) and a placebo. One-third of the subjects were randomly assigned to receive each treatment. At the end of the study, researchers recorded whether or not the subjects relapsed. Which of the following conditions must be satisfied to perform the appropriate chi-square test using the data from this study?

I. The population distribution is approximately Normal.

II. The treatments were randomly assigned.

III. The observed counts are all at least 5.

a. I only

b. II only

c. III only

d. II and III

e. I, II, and III

Select the best answer.