EXAMPLE 15.13 Plotting the group Means

CASE 15.1 The means for the promotions and discount data of Case 15.1 are plotted in Figure 15.7. We have chosen to put the two values of promotion on the x axis. We see that the mean expected price for the 40% discount condition is consistently lower than the mean expected price for the 20% discount condition. Similarly, the means for three promotions are consistently less than the means for one promotion. The two lines are approximately parallel, suggesting that there is little interaction between promotion and discount in this example.