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Sample size determination for an exponential survival model with an unrestricted covariate
Author(s) -
Zhen Boguang,
Murphy James R.
Publication year - 1994
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.4780130406
Subject(s) - covariate , sample size determination , statistics , mathematics , exponential function , range (aeronautics) , survival analysis , covariance matrix , covariance , exponential growth , sample (material) , econometrics , mathematical analysis , physics , materials science , composite material , thermodynamics
We derive formulae for estimating sample size and power for detecting the effect of an unrestricted covariate on survival time. These are useful in designing survival studies with different patterns of recruitment and follow‐up when survival time is exponentially distributed. We use the asymptotic covariance matrix, conditional expectation and Taylor's expansion techniques to develop these formulae. Computer simulations indicate that the asymptotic approximations used in developing the formulae are good over a range of parameter values and different patterns of recruitment and follow‐up that are relevant to survival studies.