comparable, so that accurate comparisons can be made of smoking rates. However, the sampling procedure failed to yield comparable samples. In fact, the differences between the samples were striking and furthermore, would systematically lead to an underestimation of true smoking prevalence at Indiana University in 2009. Table 1 reveals the differences in the two samples. The differences are striking. In 2007, the proportion of males in the Indiana University sample was 42.4%. In 2009, it was 37.6%. In 2007, the percentage of freshman in the sample was 19.5%. In 2009, the percentage of freshman was 26.9%. The percentage of students living in residence halls increased from 26.8% to 33.8%. Anyone looking at these differences can easily see that the study conclusions are invalid. The same reasoning that led to the conclusion that the smoking rate dropped would lead to the conclusion that the percentage of males dropped and that the percentage of freshman dropped and that the percentage of students living in residence halls dropped as a result of the tobacco-free policy. But it is obviously not true that the tobacco ban led to a decline in the percentage of male students at Indiana University or that it led to fewer freshmen or fewer students living in residence halls. In order to draw such conclusions, one would need comparable samples. The study failed to achieve that. In fact, the differences in the samples would - in each case - lead to an underestimation of smoking prevalence at Indiana University in