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Naslov dogodka: Testing KaplanMeier curves against an alternative of concave or convex nonproportional hazards
Datum dogodka: petek, 31. maj 2019  13:00 Lokacija predavanja: IBMI Predavatelj: dr. John O'Quigley, University of ParisSorbonne We show the optimality of the logrank test for comparing two groups when the hazards are proportional. When they are not proportional we can see that this optimality is lost. Many authors have considered alternatives to the logrank in situations of nonproportionality. We recall this work before considering two subclasses of nonproportional hazards  concave and convex nonproportional hazards. Although less broad than just nonproportional hazards, the two classes represent a very large class of possibilities. We will see that situations such as delayed effect (immunotherapy trials), situations of nonresponders and situations of group attribution errors all belong to these classes. For these two classes, optimal tests can be identified theoretically although, in practice, are not typically available. Nonetheless we describe tests that are close to optimal for the concave and convex classes. Some practical concerns are described. These include efficiency losses and sample size calculation for concave and convex alternatives to the null.
