Consider the following remission times of 42 patients with acute leukemia reported by Freireich et al. (1963)* in a clinical trial to assess the efficacy of 6-mercaptopurine (6-MP) to maintain remission. The patients were randomized to receive 6-MP or a placebo. The study was terminated after 1 year and the following remission times, in weeks, were recorded: 6-MP (21 patients): 6, 6,6, 7, 10,13, 16, 22, 23, 6+, 9+, 10+, 11+, 17+, 19+, 20+, 25+, 32+, 32, 34+, 35+ Placebo (21 patients): 1, 1, 2, 2, 3, 4, 4,5, 5, 8, 8, 8, 8, 11,11, 12, 12, 15, 17, 22, 23 

(a) Compute and plot the PL estimates of S(t) for the two treatment groups? 

(b) Estimate the median remission time for each treatment group. 

(c) Compute and plot the Nelson-Aalen estimates of S(t) for the two treatment groups. Compare the estimates with the PL estimates. 

(d) Estimate the median remission time for each treatment group. Compare the median remission time with that obtained using the PL method.

Answer rating: 100% (QA)

a To compute the PL estimates of St for the two treatment groups we first need to order the remission times in ascending order and then calculate the number of failures ie patients who experienced a r... View the full answer