15.73 Catherine Tate owns a restaurant in Maltby Street Market, London, and serves four different main dishes.

She randomly recorded the time (in hours) spent at her restaurant by customers, grouped according to their age, who order the different dishes—20 years or younger, 21 to 40 years, and 41 years or older. Her observations are recorded in the following table.

Time Spent (in hours)

Main Dishes < 20 21 to 40 > 40 1 2 2.1 1.5 0.4 0.3 0.5 3 1.8 2.5 2.8 2 1.4 2 2.8 1.5 3.2 2.4 2.6 1.5 1.1 4 1.6 3.2 1.5 2 3 2.7 1.6 2.1 3.5 0.4 2.1 3.1 2.3 1.4 0.6 0.7 3.1 4 3.5 1.6 0.5 0.8 1.5 1.1 2.1 1.5 2.1 1.3 0.8 2.1

a. Prepare the complete analysis of variance table for the record.

b. Justify which of the main effects are significant at the 5% significance level.

c. Is the interaction effect significant at the 5%

significance level?