For each exercise, perform these steps. Assume that all variables are normally or approximately normally distributed.

a. State the hypotheses and identify the claim.
b. Find the critical value(s).
c. Compute the test value.
d. Make the decision.
e. Summarize the results.
Use the traditional method of hypothesis testing unless otherwise specified.

At a large local hospital 20 teen volunteers worked a total of 172 hours with a standard deviation of 3.6. Thirty senior citizen volunteers worked a total of 366 hours with a standard deviation of 4.2. At α = 0.01, can a difference in means be concluded?