In a sample of 49 adolescents who served as subjects in an
immunologic study one variable of interest was the diameter of skin
test reaction to an antigen. The sample mean and standard deviation
were 21 and 11 mm erytheme, respectively. Can it be conclude from
these data that the population mean is less than 30? let α=.05.
Assume that the population standard deviation is 12.2 Please sketch
the rejection region?