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From | Roger Harbord <rogerharbord@bigfoot.com> |
To | statalist@hsphsun2.harvard.edu, turnere@ohsu.edu |
Subject | st: Re: st: survival analysis: given median survival time � 95% CI, how does one calculate SE, t, or exact p? |
Date | Sun, 22 Oct 2006 09:44:15 +0100 |
Dear Stata users,
I am working with a report of data analyzed using survival analysis.
Specifically, the survival probabilities were calculated using the Kaplan-Meier method, and the estimated survival distributions were compared between groups using the log-rank test.
For each group, they report the N, median survival time, and the 95% CI around the median. (The CIs were not calculated using a simple 1.96 x SE, because the upper and lower CI widths are different from one another.)
They also report exact P values, but only for where they get a value under .05.
Where the comparison between groups is nonsignificant, they just report "NS".
My goal is to find the exact P value (which I can get to if I can first get SE or t).
Would someone know how I can achieve this using Stata or some not-too-difficult formula?
Thank you.
Erick
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