Hi, I have the same question as Jason on how to estimate the standard error and construct CI around S_1(t) - S_2(t). From summary.survfit(obj), how can I combine the 2 survival estimates and the associated standard errors, to get an estimate of standard error for the difference / then calculate CI?
For example, my summary(obj) gave me: treatment=0 time n.risk n.event survival std.err lower 95% CI upper 95% CI 10.0000 69.0000 28.0000 0.7313 0.0438 0.6504 0.8223 treatment=1 time n.risk n.event survival std.err lower 95% CI upper 95% CI 10.0000 86.0000 10.0000 0.9055 0.0285 0.8514 0.9631 The S_1(t=10) - S_2(t=1) = 0.9055-0.7313 = 0.1742. how to calculate the standard error this difference based on SD_1 = 0.0438 and SD_2 = 0.0285, and then the 95% CI for the difference? Thanks John ________________________________ From: Thomas Lumley <tlum...@uw.edu> To: Jason Connor <jcon...@alumni.cmu.edu> Cc: r-help@r-project.org Sent: Wednesday, March 7, 2012 10:58 AM Subject: Re: [R] Difference in Kaplan-Meier estimates plus CI On Thu, Mar 8, 2012 at 4:50 AM, Jason Connor <jcon...@alumni.cmu.edu> wrote: > I thought this would be trivial, but I can't find a package or function > that does this. > > I'm hoping someone can guide me to one. > > Imagine a simple case with two survival curves (e.g. treatment & control). > > I just want to calculate the difference in KM estimates at a specific time > point (e.g. 1 year) plus the estimate's 95% CI. The former is > straightforward, but the estimates not so much. > > I know methods exist such as Parzen, Wei, and Ying, but was surprised not > to find a package that included this. > > Before I code it up, I thought I'd ask if I was just missing it somewhere. summary.survfit() in the survival package will give you the point estimate and standard error, and then combining these into a difference and confidence interval for the difference is easy. -thomas -- Thomas Lumley Professor of Biostatistics University of Auckland ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]]
______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
