You are given the following information obtained from a random sample of 5 observations. Assume the population has a normal distribution.

20 18 17 22 18

You want to determine whether or not the mean of the population from which this sample was taken is significantly less than 21.

a. State the null and the alternative hypotheses.
b. Compute the standard error of the mean.
c. Determine the test statistic.
d. Determine the p-value and at 90% confidence, test whether or not the mean of the population is significantly less than 21.