Sample Size Planning

Sample size planning is the systematic approach to selecting an optimal number of participants to include in a research study so that some specified goal or set of goals can be satisfied. Sample size planning literally addresses the question “What size sample should be used in this study?” but an answer to the question must be based on the particular goal(s) articulated by the researcher. Because of the variety of research questions that can be asked, and the multiple inferences made in many studies, answering this question is not always straightforward. The appropriate sample size depends on the research questions of interest, the statistical model used, the assumptions specified in the sample size planning procedure, and the goal(s) of the study. In fact, for each ...