Too Many Significance Tests

A study published in April 2008 (link) reported that a pregnant woman's diet could influence the gender of her baby. A particular claim was that eating breakfast cereals increased the probability of having a boy. A Science Daily piece from Jan. 17, 2009 reports on a recently published explanation that indicates the earlier result is easily explained by chance.

According tot he Science Daily article, 132 food items were tested during two different time periods, for a total of 264 statistical tests. At a 0.05 level of significance, this number of tests would lead to, on average, 13 false positives (Type I error: rejecting the null hypothesis when the null hypothesis is indeed true).