Rosenthal, RobertRubin, Donald2014-02-191991Rosenthal, Robert. 1991. "Further Issues in Effect Size Estimation for One-Sample Multiple-Choice-Type Data." Psychological Bulletin 109, No. 2: 351-352.0033-2909http://nrs.harvard.edu/urn-3:HUL.InstRepos:11718210This article discusses models underlying the use of 1-sample effect size indicators that permit the comparison of effect sizes obtained from different multiple-choice studies by indexing all studies to the results that would have been obtained if there had been only 2 choices. The effect size indicator, the proportion index, (II), is based on a model implying that the probability of knowing a correct response will decrease as more incorrect choices are offered. For specific applications other models may be more appropriate but, for most applications they have encountered, the authors prefer and recommend their model.en-USJournal Article2014-01-29Rosenthal, Robert10.1037//0033-2909.109.2.351