A random sample of the birth weights of 186 babies has a mean of 3,103 g and a standard deviation of 696 g (based on data from "Cognitive Outcomes of Preschool Children with Prenatal Cocaine Exposure," by Singer et al., Journal of the American Medical Association, Vol. 291, No. 20). These babies were born to mothers who did not use cocaine during their pregnancies. Further, a random sample of the birth weights of 190 babies born to mothers who used cocaine during their pregnancies has a mean of 2,700 g and a standard deviation of 645 g.

a) Set up the null and alternative hypotheses to test the claim that both samples are from the populations having the same standard deviation.

b) Perform the hypothesis test you set up in (a) with the significance level αα = 0.05.

c) Using the results of (b), does cocaine use appear to affect the birth weight of a baby? Substantiate your conclusion.