Zoloft is a drug used to treat obsessive-compulsive disorder (OCD). In randomized, double-blind clinical trials, 926 patients diagnosed with OCD were randomly divided into two groups.

Subjects in group 1 (experimental group) received 200 milligrams per day (mg/day) of Zoloft, while subjects in group 2 (control group) received a placebo. Of the 553 subjects in the experimental group, 77 experienced dry mouth as a side effect. Of the 373 subjects in the control group, 34 experienced dry mouth as a side effect.

(a) What type of experimental design is this?

(b) What is the response variable?

(c) Do a higher proportion of subjects experience dry mouth who are taking Zoloft versus the proportion taking the placebo?

Use the α = 0.05 level of significance.