When the level of hemoglobin in the blood is too low, the person is anemic. Unusually high levels of hemoglobin are undesirable as well and can be associated with dehydration. A study by the Harvard Medical School Cardiogenomics Group recorded the hemoglobin levels, in grams per deciliter (g/dL) of blood, in patients undergoing cardiac surgery. A random sample of 20 male cardiac patients yielded a mean of 12.35 g/dL and a standard deviation of 2.8 g/dL. Required:
At the a = 0.05 significance level, test whether the population mean hemoglobin level for males undergoing cardiac surgery differs from 13.8 g/dL.