Table refers to a clinical trial comparing a new drug (d = 1) with a standard drug (d = 0) for subjects suffering mental depression. Initial severity of depression was recorded as mild (s = 0) or...

Table refers to a clinical trial comparing a new drug (d = 1) with a standard drug (d = 0) for subjects suffering mental depression. Initial severity of depression was recorded as mild (s = 0) or severe (s = 1). In each group, subjects were randomly assigned to one of the two drugs. Following t = 1 week, 2 weeks, and 4 weeks of treatment, each subject’s level of mental depression was classified as normal (yt = 1) or abnormal (yt = 0).

a. With scores (0, 1, 2) for t and exchangeable working correlation and permitting a d × t interaction, we obtain the GEE results shown next. Find and interpret the estimated time effect for each drug.

b. Explain why at time t, the estimated odds of normal response with the new drug are exp(−0.059 + 1.017t)times the estimated odds for the standard drug, for each initial diagnosis level. Interpret.