I need to calculate the sample size required for an observational study in which incidence of disease is 19-29%. Population affected is 600,000 people.
The study has two samples similar on baseline characteristics treated with two different drugs.
Statistical analysis will be chi-square and Fisher's test. I have to demonstrate non-inferiority of one drugs with respect of the other one. I don't have any other info.
Can anyone help me to calculate the sample sizes required in order to obtain power of 0.80 with an alpha 0.05?
Thanks a lot in advance