Question 4:

A randomized clinical trial enrolled 42 female patients that had completed treatment for bulimia whose scores on the Eating Disorders Examination indicated that they were abstinent from binge eating and purging, and were therefore considered to be treated successfully.Subjects were randomly assigned either to receive either a medication called desipramine or a placebo. The time (months) to relapse of binge eating and purging was recorded for each subject.

a)Use the Kaplan-Meier curves to estimate the median time until relapse in each treatment group. (see attached picture).

b)Explain the hypotheses and conclusion of the log-rank test.

c. A Cox-Regression was used to model the ln(hazard) as a function of the treatment group. Here is part of the output

1. 

Overall Comparisons Chi- Square Log Rank (Mantel-Camp 14 793 1 Text of equality of survival distributions for the different levels of Treatment Survival Functions 1.0 Treatment intervention placebo intervention-censored 08 placebo-censored Cum Survival 10 00 20 00 30.00 40100 survival time (wks)Variables in the Equation B SE Wald df Sig. Exp(B) Treatmen 1.509 .410 13.578 1 .000 4.523 t