For example, if the purpose of the study is illustrative, an appropriate basis for site selection could be typical, representative, or cluster; the case studies would be conducted concurrently with other methods used in the main study; prestructuring or guidance to the evaluators in the field would be low to moderate to permit the thickness and richness of insights needed; data could be qualitative only or both qualitative and quantitative; the case studies probably would be analyzed within sites only; and the reporting would probably be narrative.
It's a very simple study with only one approach.