In the paper "Outcomes at School Age After Postnatal Dexamethasone Therapy for Lung Disease of Prematurity" (New England Journal of Medicine, Vol. 350, No. 13, pp. 1304-1313), T. Yeh et al. studied the outcomes at school age in children who had participated in a doubleblind, placebo-controlled trial of early postnatal dexamethasone therapy for the prevention of chronic lung disease of prematurity.
One result reported in the study was that the control group of 74 children had a mean IQ score of 84.4 with standard deviation of 12.6, whereas the dexamethasone group of 72 children had a mean IQ score of 78.2 with a standard deviation of 15.0. Do the data provide sufficient evidence to conclude that early postnatal dexamethasone therapy has, on average, an adverse effect on IQ? Perform the required hypothesis test at the 1% level of significance.