suppose I have an output of survival probabilities over time as follows:

Jan: .987
Feb: .962
Mar: .943
Apr: .894

What is the correct way to calculate conditional survival probability? For example, the probability of surviving to February given you have survived through January? Is it simply .962/.987 = .975?
This number is close to my observed value which is good, but it starts to get less accurate over the rest of the months.

Is March going to be .943/.975=.967, and april is going to be ..894/.967? Those numbers dont seem to be accurate to me and the further I get out, the more inaccruate the probabilities become


1 Answer 1


Actually, the probability for March given Feb is 0.943/0.962 or about 0.980 So Survival(March) = Survival(Jan) * S(F|J) * S(M|F) = 0.987 * 0.975 * 0.980 which comes out to the 0.943 provided


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