We want to carry out a survey to assess perceptions of quality and access to medical education of last year students. Based on our research, we have decided that a two stage stratified cluster sample suits our needs in terms of costs and logistics. We have 37 medical institutions in the country so the first stage will be stratified and will have 4 strata:
- Strata 1 - Public and Urban
- Strata 2 - Public and Rural
- Strata 3 - Private and Urban
- Strata 4 - Private and Rural
The institutions in each strata will be selected randomly with the number of institutions to be selected from each stratum proportional to the total stratum size. For the second stage we will randomly select a number of students from registry lists.
How do you calculate the needed sample size (number of PSUs and SSUs)? (I am using Stata.)