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Sample Size Calculation for Logrank Tests in PASS

There are a variety of procedures in PASS for examining sample size and power for the comparison of two survival curves using the Logrank test. The procedures differ by the assumptions that are made about the survival curves, the research article the procedure is based upon, and the way the survival parameters are specified. In PASS, there are four procedures that allow complete flexibility of survival curve, accrual, and loss-to-follow-up specification for the Logrank test. These four procedures differ only in the way the survival rates are specified. Hazard rates, median survival times, proportion surviving, and mortality rates are each simple functions of any of the others. You may wish to use the procedure that specifies the survival rates in a way that is reported in previous studies or your preliminary studies. Or you can convert among rates using the Survival Parameter Conversion Tool. In this video, we will use the procedure where Hazard Rates are specified directly. There will be two examples that follow. In the first example, the study design will be less complex than the second. The purpose of the first example will be to give a feel of the basic parameters that are needed to estimate a sample size for a Logrank test. The second example will extend the first example to examine the flexibility of this PASS procedure to account for more complex aspects of the designs that commonly occur.