R4.

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 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. Assume that the samples come from normal populations.

Firstborn

107.1 92.7 104 97 143.2

93.5 118.6 109.1 96.1 110.2

Secondborn

115.4 116.4 101.9 116.4 112.2

117.4 105.8 102.6 131.1 122

Can you conclude that the standard deviation of IQ is greater for the firstborn than the secondborn? Let SD 1 denote the standard deviation in the IQs of firstborn sons. Use the a = 0.05 level.

Part 1/5

State the null and alternate hypotheses.

H0: SD1 = SD2

H1: SD1 > SD2

This hypothesis test is a right-tailed test.

Part 2/5

Find the critical value. Round the answer to at least two decimal places.

The critical value is