Sample Size Calculator  ChiSquared Test  TwoSample TTest  Poisson Means  Survival Times
Question: Does the average survival time differ across two groups?
sample count  average survival time  Confidence interval (mean survival time)  

Confidence level:  95%

If the experiment is repeated many times, the confidence level is the percent of the time each sample's average survival time will fall within the reported confidence interval.
It is also the percent of the time no difference will be detected between the two groups, assuming no difference exists.
If you like this, check out Wizard — an intuitive desktop statistics package for Mac.