Bone density in newborns. In a study of maternal cigarette smoking and bone density in newborns, 77 infants of mothers who smoked had a mean bone mineral content of 0.098 g/cm3 (s1 = 0.026 g/cm3).

The 161 infants whose mothers did not smoke had a mean bone mineral content of 0.095 g/cm3

(s2

= 0.025 g/cm3).l

(a) Calculate the 95% confidence interval for μ1

− μ2

.

(b) Chapter 10 included a section on the relationship between hypothesis testing and confidence intervals. We know that if the

(1 − α)100% confidence interval excluded the value of the parameter specified under the null hypothesis, the null hypothesis would be rejected at the α-level of significance. If the value specified in the null hypothesis was included in the midst of the (1 − α)100% confidence interval, the null hypothesis would be retained at the α threshold. Based on the confidence interval you just calculated, would you reject or retain H0 : μ1 −
μ2 = 0 at α = 0.05?