Go to a journal specifically designed for Public Health (e.g., American Journal of Public Health, Public Health Reports, Journal of Public Health, Journal of Community Health, etc.) and find a study that uses:
an experimental design a quasi-experimental design a qualitative research design (specify the type - phenomenology, grounded theory, ethnography. etc.) For each article, explain explain the specific type of design employed, the sampling technique that was used, and whether the author(s) explained how they controlled for internal and external validity.