Refer to Disk drive service Problem 19.16. Assume that ANOVA model (19.23) is applicable.
a. Prepare an estimated treatment means plot. Does your graph suggest that any factor effects are present? Explain.
b. Obtain the analysis of variance table. Does anyone source account for most of the total variability? Explain.
c. Test whether or not the two factors interact; use a = .01. State the alternatives, decision rule, and conclusion. What is the P-value of the test?
d. Test whether Or not main effects for technician and make of drive are present. Use a = .01 in each case and state the alternatives, decision rule, and conclusion. What is the P-value of each test? Is it meaningful here to test for main factor effects? Explain.
e. Obtain an upper bound on the family level of significance for the tests in parts (c) and (d); use the Kimball inequality (19.53).
f. Do the results in parts (c) and (d) confirm your graphic analysis in part (a)?
Problem:
Disk drive service. The staff of u service center for electronic equipment includes three technicians who specialize in repairing three widely used makes of disk drives for desktop computers. It was desired to study the effects of technician (factor A) and make of disk drive (factor B) on the service time. The data that follow show the number of minutes required to complete the repair job in a study where each technician was randomly assigned to five jobs on each make of disk drive.
a. Obtain the fitted values for ANOVA model (19.23).
b. Obtain the residuals.
c. Plot the residuals against the fitted values. What departures from ANOVA model (19.23) can be studied from this plot? What are your findings?
d. Prepare a normal probability plot of the residuals. Also obtain the coefficient of correlation between the ordered residuals and their expected values under normality. Does the normality assumption appear to be reasonable here?
e. The observations for each treatment were obtained in the order shown. Prepare residual sequence plots and analyze them. What are your findings?