Table 4.19 shows results of a study about Y = whether a patient having surgery with general anesthesia experienced a sore throat on waking (1 = yes) as a function of D = duration of the surgery (in minutes) and T = type of device used to secure the airway (0 = laryngeal mask airway, 1 = tracheal tube).

a. Fit a main effects model using these predictors. Interpret parameter estimates.

b. Conduct inference about the D effect in (a).

c. Fit a model permitting interaction. Report the prediction equation for the effect of D when (i) T = 1, (ii) T = 0. Interpret.

d. Conduct inference about whether you need the interaction term in (c).