I tried to reproduce in stata the calculation needed for the following case:
I need to determine the sample size, required to detct the presence of
disease in a population.
The formula is rather complex so it is difficult to paste in here,
For example i need to detect with 95% confidence the abscence of disease in
a population where the presumed prevalence would be 20%. How lrge a sample
size do I need to be 95% certain that the population is free from disease.
I used a program "Winepiscope" freeware, that calculated a samplesize of 14.
in stata i tried : sampsi 0.2 0, power(0.9) onesample
and I get a result of :16
Can stata handle this type of calculation?
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