Question

classify the following study. a study determines whether taking aspirin regularly helps to prevent heart attacks. a large group of male physicians of comparable health were randomly assigned equally to taking an aspirin every second day or to taking a placebo. after several years, the proportion of the study participants who had suffered heart attacks in each group was compared. observational study experiment survey

Explanation:

In an experiment, researchers actively manipulate variables (here, giving aspirin or placebo). The participants are randomly assigned to groups. In an observational study, no manipulation occurs; researchers just observe. A survey involves asking questions. Here, since the researchers assigned the participants to take aspirin or placebo (manipulated the treatment), it's an experiment.

Answer:

Experiment