Question: An article in Science News (1 June 1996, 149, p. 345) claimed that "evidence suggests that regular consumption of milk may reduce a person's risk of stroke, the third leading cause of death in the United States." The claim was based on an observational study of 3150 men, and the article noted that the researchers "report strong evidence that men who eschew milk have more than twice the stroke risk of those who drink 1 pint or more daily." The article concluded by noting that "those who consumed the most milk tended to be the leanest and the most physically active." Go through the list of seven "reasons two variables may be related," and discuss each one in the context of this study.