hi im conducting a study on a certain ratio in a blood exam (lets call it X) .
I aim to say that there is a certain sensitivity (let say>80%) for people to be sick if X>10. (my actual intent is to check the sensitivity for different values of X)
its a retrospective cohort and the estimated incidence of sick people in the whole group is 3.5%
how or which tool should i use to calculate the sample size? i have tried to find an answer online (including this good chinese site: http://www.statstodo.com/StatsToDoIndex.php#Sample Size) but so far no success
(type 1 error 0.05 power 0.8)
