Practical
exercise 4
In this exercise we will use the log-rank test to investigate whether the mortality is significantly different in various groups of melanoma patients.
As described in practical exercise 1, you may read the data into R by the command:
melanoma=read.table("http://www.uio.no/studier/emner/matnat/math/STK4080/h08/computing/melanoma.txt",
header=T)
a) You may test the hypothesis that the mortality is the same for the two genders by the command:
survdiff(Surv(lifetime,status==1)~sex, data=melanoma)
Perform the command and interpret the results. (Remember to attach the survival library.)
b) Test whether the mortality is the same for patients with ulceration present and absent.
c) Test
whether the mortality is the same for patients in the three thickness groups 0-