Pizza ratings. Manufacturers of frozen foods often reformulate their products to maintain and increase customer satisfaction and sales. So they pay particular attention to evaluations of their products in comparison to their competitors’

products. Frozen pizzas are a major sector of the frozen food market, accounting for $2.84 billion in sales in 2007 (www.aibonline.org/resources/statistics/2007pizza.htm).

The prestigious Consumer’s Union rated frozen pizzas for flavor and quality, assigning an overall score to each brand tested. A regression model to predict the Consumer’s Union score from Calories, Type (1 cheese, 0 pepperoni), and fat content gives the following result:

a) What is the interpretation of the coefficient of Type in this regression? According to these results, what type would you expect to sell better—cheese or pepperoni?

b) What displays would you like to see to check assumptions and conditions for this model?

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Dependent variable is: Score R-squared 28.7% R-squared (adjusted) = 20.2% s 19.79 with 29 4 25 degrees of freedom Source Sum of Squares df Mean Square F-ratio Regression 3947.34 Residual 9791.35 Variable Coeff 3 1315.78 25 391.654 3.36 SE (Coeff) t-ratio P-value Intercept -148.817 77.99 -1.91 0.0679 Calories Type Fat 0.743023 0.3066 2.42 0.0229 15.6344 8.103 1.93 0.0651 -3.89135 2.138 -1.82 0.0807