Return to the CD4 data introduced from Exercise 11.4. (a) Extend the model in Exercise 12.2 to allow for varying slopes for the time predictor. (b) Next fit a model that does not allow for varying...

Return to the CD4 data introduced from Exercise 11.4.

(a) Extend the model in Exercise 12.2 to allow for varying slopes for the time predictor.

(b) Next fit a model that does not allow for varying slopes but does allow for different coefficients for each time point (rather than fitting the linear trend).

(c) Compare the results of these models both numerically and graphically.