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• Office hours for 11 Apr moved to 3:30-4:20.
• The data set for hw 4.
• Hint for HW3: For question 1 part c, you need to test whether a factor with five levels has an effect, stratifying on stage. We've done something like this in class, when the factor only has two levels. In this case, you use proc lifetest with strata and an indicator for one of the factors used in the test statement. What I've asked you to do is a bit harder. In this case, create dummy variables representing four of the five levels of the factor of interest (in this case, cell type). Now use all four variables after the test statement. That is, if ct is cell type, coded as zero through 4, create ct1 taking the values 1 for cell type 1 and 0 otherwise, and similarly construct ct2, ct3, and ct4 for types 2 through 4 respectively, and use test ct1 ct2 ct3 ct4; in conjunction with strata.
• Also, I didn't specify alpha for problem 2. Use alpha=.025.
• Office hours for Mon 28 Feb canceled.
• The format of the data file for HW3 appears to have been changed. Refer to the documentation for the correct position of the variables.
• The documentation ordered for the course and listed on the course information page is unfortunately no longer available. You can get similar information online.
• A student called to my attention that SAS versions 8 and 9 give different results for some calculations I offered in class. Specifically, Version 9 allows SAS to calculate internally transformed confidence intervals for survival curves. In class I did this using PROC PHREG. Unfortunately, the default that Version 9 uses is different from what you get from Version 8. Specifically, Version 9 uses as the default the complementary log-log transform, while Version 8 used no transformation. Hence if the data set mydata contains two variables, t a time variable and s a status variable, taking the values 0 for censored and 1 for event, then the code
  proc lifetest data=mydata outsurv=a; time t*s(0); run; puts into a confidence intervals on the original scale in version 8, but on the log log scale in version 9. To get confidence intervals on the original scale in version 8,do
  proc lifetest data=mydata; survival out=a conftype=linear; time t*s(0); run;
• Solutions for exam 1 are available.
• Office hours are 4:30-5:20 Monday and Thursday, and 10:30-11:20 Wednesday, starting immediately.
• A final exam from last year is available to help students know what format to expect on the final.

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