There is a wide range of non-probability designs that include case-control studies, clinical trials, evaluation research designs, intercept surveys, and opt-in panels, to name a few.
More recently, concerns about coverage and nonresponse coupled with rising costs, have led some to wonder whether non-probability sampling methods might be an acceptable alternative, at least under some conditions.
Propensity score adjustment is probably the most well known of these techniques.
Sections 7 and 8 discuss methods for assessing the precision of estimates and the concept of fitness for use.
We do not claim to have produced an exhaustive study of all possible methods or fully examined all of the literature on any one of them.