Problem: Leukemia treatment study (Exam 2021)

Eksempel

Exam June 2021, problem 3.

The table below shows the results of a study where children with leukemia are treated with a drug (6-MP) to prevent relapse. Some of the children were treated with the drug 6-MP and others got placebo. In the table, right censored observations are marked with an asterix (*).

Placebo: 1, 1, 2, 2, 3, 4, 4, 5, 5, 8, 8, 8, 8, 11, 11, 12, 12, 15, 17, 22, 23
6-MP: 6, 6, 6, 6*, 7, 9*, 10, 10*, 11*, 13, 16, 17*, 19*, 20*, 22, 23, 25*, 32*, 32*, 34*, 35*

These data are also given in Exercise 3.1 in page 126 in the course textbook, and can be
downloaded from https://www.mn.uio.no/math/english/people/aca/borgan/data/leukemia.txt.

Problem

Use commands in R to compute and plot Kaplan-Meier estimates for the placebo group and for the 6-MP group. Include in your plots also confidence intervals.

Explain how you from such a plot can find a confidence interval for the median survival time. What are the confidence intervals for the median survival times in each of the two groups?