Wilcox, Rand R.2011-02-172011-02-171981Wilcox, Rand R. (1981). A Cautionary Note on Estimating the Reliability of a Mastery Test with the Beta-Binomial Model. Applied Psychological Measurement, 5, 531-537. doi:10.1177/014662168100500411doi:10.1177/014662168100500411https://hdl.handle.net/11299/100425Based on recently published papers, it might be tempting to routinely apply the beta-binomial model to obtain a single administration estimate of the reliability of a mastery test. Using real data, the paper illustrates two practical problems with estimating reliability in this manner. The first is that the model might give a poor fit to data, which can seriously affect the reliability estimate, and the second is that inadmissible estimates of the parameters in the beta-binomial model might be obtained. Two possible solutions are described and illustrated.enArticle