A random sample of 10 students contains the following observations, in hours, for time spent studying in the week before final exams:
28 57 42 35 61 39 55 46 49 38
Assume that the population distribution is normal.
a. Find the sample mean and standard deviation.
b. Test, at the 5% significance level, the null hypothesis that the population mean is 40 hours against the alternative that it is higher.