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Statistical Rules of Thumb: What We Don't Want to Forget About Sample Sizes
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by Carmen Wilson VanVoorhis and Betsy Levonian Morgan - University of Wisconsin-La Crosse
Category: Editorials & Invited Articles
In this article we highlight the statistical rules of thumb guiding the selection of sample sizes for detecting differences, associations, chi-square, and factor analyses.
Cohen (1990), as an eminent psychometrician, had the experience and depth to write an article entitled "Things I Have Learned (So Far)." However, if you are a student grappling with learning the complexities of research, you may want an article entitled "What We Need to Know." If you are faculty aiding undergraduate projects, you may wish to join us in focusing on the utilitarian principles of research design that we "don't want to forget." Concerned by the ease of computer programs that tend to lure a person into hedging on the tried-and-true of statistical theory, we were motivated to reestablish some of the solid heuristics on sample size that guide our research. Indeed, issues regarding power and effect size and their implications for sample size selection are pressing themes in research design and statistical implications (Kraemer & Thiemann; 1987; Wilkinson, 1999; Wolins, 1982). Consequently, we offer this concise review and summary of the "rules of thumb" regarding sample size in the spirit of improving research design and aiding our students in their research...