ERIC Number: ED201665
Record Type: RIE
Publication Date: 1981-Apr
Reference Count: 0
A Method for Comparing Test Difficulties.
Frisbie, David A.
The relative difficulty ratio (RDR) is used as a method of representing test difficulty. The RDR is the ratio of a test mean to the ideal mean, the point midway between the perfect score and the mean chance score for the test. The RDR tranformation is a linear scale conversion method but not a linear equating method in the classical sense. The transformation is used with non-parallel tests, tests which may differ in both item format and length. The goal of the transformation is not to "equate" for differences in test difficulty. The purpose of the RDR transformation is to convert the raw score scale from a given test so that the new scale has the same mean chance point and the same range or length as the raw score scale from a second test. The goal is to eliminate differential guessing chance factors and unequal test lengths as competing explanations for why two test means are different (or the same). A method for transforming one of the raw score scales so that an inferential test of mean differences can be accomplished though the original raw score scales vary in mean chance score and/or length is described. (RL)
Publication Type: Speeches/Meeting Papers; Reports - Research
Education Level: N/A
Authoring Institution: N/A
Identifiers: Relative Difficulty Ratio
Note: Paper presented at the Annual Meeting of the National Council on Measurement in Education (Los Angeles, CA, April 11-17, 1981).