Thank you so much for your answer.
It is a retrospective study (observing past information) and we need to determine the % of the persistence of a drug use at a one-year since the first dispensation.
I already determine the sample size, but I was asked if it is really necessary, considering the...
I am planning to do an observational study in which it is intended to analyze the dispensation in pharmacies of a certain drug.
I will have access to the entire dispensing database for this drug, is it necessary to determine the sample size?
If calculation is not necessary, how...
I would like to ask your help on the decision about the best methodology to determine the sample size to conduct an observational study.
This is a study to be carried out by a pharmaceutical company in which it is intended to characterize all combinations of drugs used before...