Exercise 1.21 presented a study comparing forced expiratory volume after 1 hour of treatment for three drugs

(a,

b, and p = placebo), adjusting for a baseline measurement x1. Table 4.1 shows the results of fitting some normal GLMs (with identity link, except one with log link) and a GLM assuming a gamma response. Interpret results.

Table 4.1 Results of Fitting GLMs for Exercise 4.32 Explanatory Variables R2 AIC Fitted Linear Predictor base 0.393 134.4 0.95 + .90x1 drug 0.242 152.4 3.49 + .20b − .67p base + drug 0.627 103.4 1.11 + .89x1 + .22b − .64p base + drug (gamma) 0.626 106.2 0.93 + .97x1 + .20b − .66p base + drug (log link) 0.609 106.8 0.55 + .25x1 + .06b − .20p base + drug + base:drug 0.628 107.1 1.33 + .81x1 − .17b − .91p + .15x1b + .10x1p