Graphs and tables are currently available for approximating the sample size needed to test the equality of two alpha reliability coefficients with desired power. These tables and graphs are limited to particular values of Type I error, power, and effect size. General formulas are derived to determine the sample size requirements for hypothesis testing with desired power and interval estimation with desired precision.
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2.
Bonett, D.G. (in press). Sample size requirement for testing and estimating coefficient alpha. Journal of Educational and Behavioral Statistics.
3.
Cronbach, L.J. (1951). Coefficient alpha and the internal structure of tests. Psychometrika, 16, 297-334.
4.
Feldt, L.S. (1965). The approximate sampling distribution of Kuder-Richardson coefficient twenty. Psychometrika, 30, 357-370.
5.
Feldt, L.S. (1969). A test of the hypothesis that Cronbach’s alpha or Kuder-Richardson coefficient twenty is the same for two tests. Psychometrika, 34, 363-373.
Feldt, L.S., & Ankenmann, R.D. (1999). Determining sample size for a test of the equality of alpha coefficients when the number of part-tests is small. Psychological Methods, 4, 366-377.
8.
Fleiss, J.L. (1981). Statistical methods for rates and proportions. New York: Wiley.
9.
Novick, M.R., & Lewis, C. (1967). Coefficient alpha and the reliability of composite measurements. Psychometrika, 32, 1-13.
10.
McGraw, K.O., & Wong, S.P. (1996). Forming inferences about some intraclass correlation coefficients. Psychological Methods, 1, 30-46.
