Over the past thirty years, the minimum education requirements set by employers have increased significantly. In particular, the proportion of jobs "requiring" a college degree has greatly increased. Amy produced the following model: "The reason for this is that college graduates are smarter." In class and in the text, three rules of thumb for model building are discussed. Of the three, which one explains best why this is a bad model? Please explain.

A television commercial states that one-third of people who vape begin smoking a year later, whereas a much smaller proportion of people who don't vape begin smoking a year later. Explain why this is an unfair comparison (a semi-attached figure).