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Dear all, I want to compare the (partially censored) survival times of two groups using the logrank test. To my surprise, I get different asymptotic p values using PROC LIFETEST from SAS or PROC TWOSAMPL from PROC StatXact. It seems as if the scores used are different between the two procedures, as the rank statistics slightly differ. Furthermore, LIFETEST obviously uses a Chi-Squared approximation, while TWOSAMPL rather uses a normal approximation. I wouldn't expect this to make much difference, though. Did anybody come across this before and can offer any explanation about the computational differences? Which scoring is to be preferred? I am willing to use the exact version of the test only if the scores used are reasonable. Of coures I'll post a summary of responses. Thanks in advance for any suggestions, Michael ***************************************************** Dr. Michael Meyners Boehringer Ingelheim Pharma GmbH & Co. KG Medical Data Services Birkendorfer Strasse 65 88397 Biberach an der Riss Germany Tel.: +49 (0)7351 54 4219 Fax: +49 (0)7351 83 4219 E-Mail: [log in to unmask] *****************************************************