Is there a difference in the yields of different types of investments? The file |33|S3 contains the

Question:

Is there a difference in the yields of different types of investments? The file |33|S3 contains the yields for a one year certificate of deposit (CD) and a five year CD for 24 banks in the United States as of June 21, 2011. (Data extracted from www.Bankrate.com, June 21, 2011.)
a. Construct a 95% confidence interval estimate for the mean yield of one year CDs.
b. Construct a 95% confidence interval estimate for the mean yield of five year CDs.
c. Compare the results of (a) and (b).