(b)Estimate the regression parameters, the number of complaints per
visit for a physician having the (sample)meanlevel of the explana-
tory factor, and draw the regression line on the same graph with the
scatter diagram.
(c) Test to see if the factor and the number of complaints per visit are
independent; state your hypotheses and choice of test size.
(d) Calculate the coe‰cient of determination and provide your inter-
pretation.8.12 Refer to the data in Exercise 8.11, but consider all four explanatory fac-
tors and the product residency training by workload simultaneously.
(a) Fit the multiple regression model to obtain estimates of individual
regression coe‰cients and their standard errors. Draw conclusions
concerning the conditional contribution of each factor.
(b)Within the context of the multiple regression model in part (a), does
the residency training alter the e¤ect of workload on the number of
complaints per visit?
(c) Taken collectively, do the five independent variables contribute sig-
nificantly to the variation in log survival times?
(d) Calculate the coe‰cient of multiple determination and provide your
interpretation.
EXERCISES 313