Daniel Brewer wrote:
I would like to do some power estimations for a log-rank two sample test
and cpower seems to fit the bill. I am getting confused though by the
man page and what the arguments actually mean. I am also not sure
whether cpower takes into account censoring or not.
Could anyone provide a simple example of how I would get the power for a
set control/non-control clinical trial where censoring occurs at an
estimated rate with an estimated drop out rate.
Quite confused about this.
cpower handles censoring by specification of an accrual and follow-up
periods and the event probability by reference time tref. I believe the
censoring distribution is assumed to be uniform, i.e., that accrual
occurs at a uniform rate.
To have more control over the situation, the simulation-based spower
function is one to look into.
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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