Question

8. Researchers have found that women who take oral contraceptives (birth control pills) are at higher risk of having a heart attack or stroke than women who do not take them. They also found that the risk is substantially higher for both groups if a woman smokes. Assume that the proportions of women who smoke are similar in both groups. In investigating the relationship between taking oral contraceptives (the explanatory variable) and having a heart attack or stroke (the response variable), explain whether smoking would fit the definition of each of the following: a. A confounding variable. b. An effect modifier. c. An interacting variable.

Answer 1

The correct answer is C.

Smoking is an interacting variable. It interacts with the birth control to increase the risk of having a heart attack or stroke rather than being the cause. It is not a confounding variable because the proportion of smokers in the two groups are the same. It is also not an effect modifier.