Breast Milk and IQ. Following are summary statistics from Exercise 16.60 on IQ for samples of children at age 71

/2–8 years who were born preterm. The researchers used the following designations. Group I: mothers declined to provide breast milk;

Group IIa: mothers had chosen but were unable to provide breast milk; and Group IIb: mothers had chosen and were able to provide breast milk. Use a family confidence level of 0.99. Here qα = 4.15.

Group nj x¯j sj I 90 92.8 15.2 IIa 17 94.8 19.0 IIb 193 103.7 15.3