Question

For each of the statistical studies described, indicate whether the study is an observational study or an experiment. Give a brief explanation for your choice. A study to evaluate whether vitamins can help prevent recurrence of blocked arteries in patients who have had surgery to clear a blocked artery was described in the article "Vitamins Found to Help Prevent Blocked Arteries" (Associated Press, September 1, 2002). The study involved 205 patients who were assigned to one of two groups. One group received a vitamin supplement for 6 months, while the other group did not receive the vitamin supplement.

Short answer

The provided study is an experiment, as the researchers manipulated the variable of interest, which was the intake of vitamin supplements.

Step-by-step solution

Identify the type of study

In the given example, the patients were divided into two groups: one that received vitamin supplements and the other that did not. Here, the variable being tested (i.e., intake of vitamin supplements) is under the researcher's control. The effects on the variable of interest (i.e., recurrence of blocked arteries) were then observed.

Make the determination

Given that the variable was manipulated by the researchers, the study can be classified as an experiment, not an observational study.