st: survival analysis: given median survival time � 95% CI, how does one calculate SE, t, or exact p?

["Erick Turner" <turnere@ohsu.edu>]

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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