Adventures in Correlation vs. Causation
I'm inordinately fond of examples of correlation that could be naively construed as causation. Examples abound, from hemlines and stock markets, to urban murder rates and doctors per capita.
Here is another one I ran across recently, and it has to do with diet cola consumption. The gist:
[The study] looked at seven to eight years of data on 1,550 Mexican-American and non-Hispanic white Americans aged 25 to 64. Of the 622 study participants who were of normal weight at the beginning of the study, about a third became overweight or obese.
Most interesting are the detailed results, which follow, and summarize the percentage likelihood of diet and non-diet cola consumers becoming obese by the end of the study:
| Cans | Regular | Diet |
| ≤ 0.5 | 26% | 36.5% |
| 0.5 - 0.9 | 30.4% | 37.5% |
| 1.0 - 1.9 | 32.8% | 54.5% |
| ≥ 2.0 | 47.2% | 47.2% |
Whoa, diet cola makes people fat! Call 60 Minutes, or Consumer Reports, right? Riiiight. 
