We focus here on potentially ambiguous and problematic 
types of sampling situations, which occur often in health 
care sampling contexts. These situations may occur and 
be addressed at a study’s design phase, and, because the 
design should determine the analysis, our discussion has 
implications for the analysis, too. Our objective is to 
provide illustrations of these situations and offer guid- 
ance for choosing more efficient and appropriate solu- 
tions to sampling design and analysis challenges.