Calculating sample size with more parameters

[May Blake]

Hello,

I am trying to calculate sample size with the parameters below. I used the code below to calculate the sample size but there is no where for me to specify the interval and event frequency. Can anyone help me figure this out. Thank you in advance.

Parameters to include;
power at 95%
the outcome frequency is 10 – 15 events per year total
effect size, 10, 15, 20
Median follow up interval of 3 years
Recruitment of 5 years


/[CODE]
power twoproportions .05 (.10 .15 .20), test(chi2) power(0.95)

[Paul Dickman]

The command is for proportions. If you have "outcome frequency is 10 – 15 events per year" then the proportion will only be 0.10-0.15 if you have 100 at baseline and a 1-year follow-up.

It's not clear how you would know the "events per year" without knowing the sample size, but if you are to use this command you need to calculate the expected proportions, which will be a function of "expected events per year" and length of follow-up. Alternatively, it seems you might have a follow-up (survival) study so use a command for calculating power for a survival design.