How do I calculate sample size for a three armed trial in which a survival analysis will be the primary analysis?

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Adrian Esterman

Another potential technique is to undertake the sample size calculation for the two arm likely to have the closest survival, but setting alpha at (say) 0.03 to allow for multiple testing. Then multiply the total sample size by 3/2.

Yevgen Bogodistov

Try the free software for a sample size calculation. GPower. A manual is also there.

http://www.gpower.hhu.de/