Breast Milk and IQ. Considerable controversy exists over whether long-term neurodevelopment is affected by nutritional factors in early life. A. Lucas and R. Morley summarized their findings on that question for preterm babies in the publication “Breast Milk and Subsequent Intelligence Quotient in Children Born Preterm” (The Lancet, Vol. 339, Issue 8788, pp. 261–264). The researchers analyzed IQ data on children at age 71

/2–8 years. The mothers of the children in the study had chosen whether to provide their infants with breast milk within 72 hours of delivery. 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. Here are the summary statistics on IQ.

Group nj x¯j sj I 90 92.8 15.2 IIa 17 94.8 19.0 IIb 193 103.7 15.3 At the 1% significance level, do the data provide sufficient evidence to conclude that a difference exists in mean IQ at age 71

/2–8 years for preterm children among the three groups? Note: For the degrees of freedom in this exercise:

α 0.10 0.05 0.025 0.01 0.005 Fα 2.32 3.03 3.74 4.68 5.39