Sample-size calculations for the Cox proportional hazards regression model with nonbinary covariates.
This paper derives a formula to calculate the number of deaths required for a proportional hazards regression model with a nonbinary covariate. The method does not require assumptions about the distributions of survival time and predictor variables other than proportional hazards. Simulations show that the censored observations do not contribute to the power of the test in the proportional hazards model, a fact that is well known for a binary covariate. This paper also provides a variance inflation factor together with simulations for adjustment of sample size when additional covariates are included in the model. Control Clin Trials 2000;21:552-560
Hsieh
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CSPCC, Department of Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA. fhsieh@mailsvr.icon.palo-alto.med.va.gov
Lavori
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D000704:Analysis of Variance; D016016:Proportional Hazards Models; D018401:Sample Size; D016019:Survival Analysis