Are you smarter than your older brother? In a study of birth order and intelligence, 1Q 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 secondbor 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. Firstborn 113 86 94 105 117 117 92 120 113 96 Secondborn 115 111 101 93 105 87 97 118 96 100 Send data to Excel Part: 0/2 Part 1 of 2 (a) Construct a 90% confidence interval for the difference in mean IQ between firstborn and secondborn sons. Let H, denote the mean IQ of the firstborn sons. Use the TI-84 calculator and round the answers to one decimal place. An 90% confidence interval for the difference in mean IQ between firstborn and secondborn sons is