1. In a sample of 49 adolescents who served as the subjects in an immunologic study, one variable of interest was the diameter of a skin test reaction to an allergen. The sample mean and standard deviation were 21 and 11 mm erythema, respectively.
a. Use the Z or t-distribution? Why?
b. One-sided or two-sided test? Why?
c. Can it be concluded from these data that the population mean is less than 24 mm erythema?
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