For what applications can probability and non-probability sampling be used?

Almost any type of sample has some utility when estimating population quantities. The focus in this paper is to indicate what type or combination of types of sampling can be used in various situations ranging from a sample designed to establish cause-effect or legal challenge to one involving a simple subjective judgment. Several of these methods have little or no utility in the scientific area but even in the best of circumstances, particularly complex ones, both probabilistic and non-probabilistic procedures have to be used because of lack of knowledge and cost. We illustrate this with a marbled murrelet example.