Recently I noticed a couple of good examples of observational studies that can be used in my future Intro Stats teaching.
1) In the Parents magazine, it reported that a study found a positive association between the frequency and severity of heartburn during pregnancy of the mom and how much hair the newborn baby has. According to the study, about two thirds of women who reported to have modest to severe heartburn during pregnancy gave birth to babies with full head of hair, while most of women who didn't have heartburn during pregnancy have babies with little hair.
2) I read on Columbia's website about a study that found positive association between the appointment of top female executives and performance of a company.
