To compare three brands of computer keyboards, four data entry specialists were randomly selected. Each specialist used all three keyboards to enter the same kind of text material for 10 minutes, and the number of words entered per minute was recorded. The data obtained are given in Table 11.11. If we use these data, SST, SSB, and SSE can be calculated to be 392.6667, 143.5833, and 2.6667, respectively.
TABLE 11.11
Results of a Keyboard Experiment

a. Test the null hypothesis H0 that no differences exist between the effects of the keyboard brands on the mean number of words entered per minute. Set α = .05.
b. Test the null hypothesis H0 that no differences exist between the effects of the data entry specialists on the mean number of words entered per minute. Set α = .05.
c. Use Tukey simultaneous 95 percent confidence intervals to make pairwise comparisons of the keyboard brand effects on the mean number of words entered per minute. Which keyboard brand maximizes the mean number of words entered per minute?

Keyboard Brand Data Entry Specialist 71 74 67 67 62 63 57 63 59 59 54