THE PRECISION OF PRACTICE ANALYSIS RESULTS IN THE PROFESSIONS

A practice analysis, in which an appropriate sample of professionals i s asked to describe what they do in their practices, is considered an essential part of the content-related validity evidence for licensure and certification tests. This article examines the precision of estima tes of the mean frequencies for categories of activities in an activit y inventory administered on two occasions about 6 weeks apart. In part icular, it explores the variability in estimates of the mean frequenci es for categories due to the sampling of respondents, activity stateme nts, and occasions. The results suggest that samples of 200 respondent s, about 10 to 20 activity statements per category, and one occasion a re adequate for estimating the mean frequency for each category.