Statistical power analysis (also referred to as sample size calculation) is a set of procedures to determine the appropriate number of participants for recruitment to a research study. Power analysis can be performed before or after the collection of data. When performed before, power analysis serves to aid researchers in their development of a desired sample size; when performed after, power analysis can reveal to researchers a reason for a nonsignificant result. In general, a power of .80 (or an 80% likelihood of rejecting the null hypothesis correctly) is acceptable, though there exists no formal standard. Many grant-awarding institutions as well as institutional review and ethics boards require power analysis and, as a result, it is most often conducted a priori, or before data are ...