Does taking large amounts of vitamins protect against cancer? To study this question, researchers recruited 10,000 people, all over the age of 50. Half of the subjects selected at random took vitamin supplements, and others took a placebo that has no active ingredient. The researchers followed all the subjects for ten years. At the end of the study, the people in the vitamin group were no less likely to have cancer than the people in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer.

what is the response variable

What is the explanatory variable