Newscientist.com ran the headline \"Breakfast Cereals Boost Chances of Conceivin
ID: 3247530 • Letter: N
Question
Newscientist.com ran the headline "Breakfast Cereals Boost Chances of Conceiving Boys, " based on an article which found that women who eat breakfast cereal before becoming pregnant are significantly more likely to conceive boys. The study used a significance level of alpha = 0.01. The researchers kept track of 133 foods, and for each food, tested whether there was a difference in the proportion conceiving boys between women who ate the food and women who didn't. Of all the foods, only breakfast cereal showed a significant difference. If none of the 133 foods actually have an effect on the gender of a conceived child, how many (if any) of the individual tests would you expect to show a significant result just by random chance? test(s) Mathews, F., Johnson, P.J., and Neil, A. (2008). "You are what your mother eats: evidence for maternal preconception diet influencing foetal sex in humans." Proceedings of the Royal Society B: Biological Sciences. 275: 1643, 1661-1668.Explanation / Answer
probability that a test will show significant effect by random chance p=0.01
hence expected of the individual test to show significant effect by random chance =np =133*0.01 =13.3 ~13 tests
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