If a larger town has 2 or moresites assigned, select each one separately. F. EPI Methodology 1. Usually requires 5 days of work for 4-6interviewers. 2. Has been used extensively to detect areas of low immunization coverage, as target areas to expand immunization programs. G. Potential Problems with EPI method 1.
Second stage departs from true random sampling.
Possible bias in not revisiting household where no one was home. To calculate confidence intervals, use Epi Info C-sample module. To make before and after comparisons, the sample size might need to be expanded. Variable cluster size or high non-response rates will need weighting 3. If nationwide estimates wanted, need multistage or possibly stratified design.