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: Utts, Jessica M.. Seeing Through Statistics (p. 114). Cengage Learning. Kindle Edition.