An article discussed the price of a market basket of items at Publix and Winn-Dixie supermarkets, and at Walmart and Super Target stores, located in South Florida. The file Supermarket- Prices contains the prices listed in that article (data extracted from "S. Salisbury, Supermarket Showdown," The Palm Beach Post, February 11, 2011, pp. 1F, 7F)
a. At the 0.05 level of significance, determine whether there is evidence of a difference in the mean prices for these items at the four supermarkets.
b. What assumptions are necessary to perform this test?
c. If appropriate, use the Tukey procedure to determine which supermarket mean prices differ. 1Use a = 0.05.2
d. Was there a significant block effect in this experiment? Explain.