EXAMPLE 15.11 Plotting the Data

CASE 15.1 With 10 observations per treatment, we can plot the individual observations. To do this, we created an additional variable, “Comb,” that has four distinct values corresponding to the particular combination of the number of promotions and the discount. The value “d20-p1” corresponds to 20% discount with one promotion, and the values “d20-p3,” “d40-p1,” and “d40-p3” have similar interpretations. The data are plotted in Figure 15.5. The lines in the figure connect the four group means.