Are you smarter than your older brother? In a study of birth order and intelligence, IQ tests were given to 18- and 19-year-old men to estimate the size of the difference, if any, between the mean IQs of firstborn sons and of secondborn sons. The following data for 10 firstborn sons and 10 secondborn sons are consistent with the means and standard deviations reported in the article. It is reasonable to assume that the samples come from populations that are approximately normal. Can you conclude that the mean IQ of firstborn sons is less than the mean IQ of secondborn sons? Let mu, denote the mean IQ of firstborn sons and mu2 denote the mean IQ of secondbor sons. Use the alpha = 0.05 level and the P-value method with the TI-84 Plus calculator. Firstborn
107 113 84 126 99
95 98 109 91 90
Secondborn
112 92 102 86 97
106 105 116 109 95