In a local community there are three grocery chain stores.

The three have been carrying out a spirited advertising campaign in which each claims to have the lowest prices.

A local news station recently sent a reporter to the three stores to check prices on several items. She found that for certain items each store had the lowest price. This survey didn’t really answer the question for consumers. Thus, the station set up a test in which 20 shoppers were given different lists of grocery items and were sent to each of the three chain stores. The sales receipts from each of the three stores are recorded in the data file Groceries.

a. Why should this price test be conducted using the design that the television station used? What was it attempting to achieve by having the same shopping lists used at each of the three grocery stores?

b. Based on a significance level of 0.05 and these sample data, test to determine whether blocking was necessary in this example. State the null and alternative hypotheses. Use a test-statistic approach.

c. Based on these sample data, can you conclude the three grocery stores have different sample means?
Test using a significance level of 0.05. State the appropriate null and alternative hypotheses. Use a p-value approach.

d. Based on the sample data, which store has the highest average prices? Use Fisher’s LSD test if appropriate.