In 2007, the United States experienced the biggest jump in food prices in 17 years (The Wall Street Journal, April 1, 2008). A variety of reasons led to this result, including rising demand for meat and dairy products in emerging overseas markets, increased use of grains for alternative fuels, and bad weather in some parts of the world. A recent survey compared prices of selected products at grocery stores in the Boston area. The accompanying table shows the results.

In a report, use the sample information to:
1. Determine whether differences exist in the average prices of products sold at the three stores at the 5% significance level.
2. Determine whether differences exist in the average prices of the 11 products at the 5% significance level.
3. If differences exist between the average prices of products sold at the three stores, use Tukey's HSD method to determine which stores' prices differ.

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Item Two-liter Coke Doritos chips Cheerios cereal Prince spaghetti Skippy peanut butter Cracker Barrel cheese Pepperidge Farm white bread Oreo cookies One dozen eggs* Coffee* Gallon of milk* Crosby's $1.79 4.29 3.69 1.59 5.49 4.99 3.99 Shaw's $1.59 4.99 2.99 1.69 4.49 4.99 3.99 Market Basket $1.50 3.50 3.00 1.99 3.99 3.49 3.99 4.69 2.49 4.49 3.69 3.39 2.69 4.79 3.19 3.00 1.59 3.99 1.59