ERIC Number: ED216013
Record Type: Non-Journal
Publication Date: 1981-Nov
Reference Count: N/A
Unbiased Estimators of Ability Parameters, of Their Variance, and of Their Parallel-Forms Reliability.
Lord, Frederic M.
This paper is primarily concerned with determining the statistical bias in the maximum likelihood estimate of the examinee ability parameter in item response theory, and of certain functions of such parameters. Given known item parameters, unbiased estimators are derived for (1) an examinee's ability parameter and proportion-correct true score; (2) the variance of ability parameters across examinees in the group tested, and the variance of proportion-correct true scores; and (3) the parallel-forms reliability of the observed test score, the maximum likelihood estimator. These formulas apply in situations where the item parameters are known; they are not adequate for situations where the item parameters and ability parameters are estimated simultaneously from a single data set. (Author/BW)
Publication Type: Reports - Research
Education Level: N/A
Sponsor: Office of Naval Research, Arlington, VA. Personnel and Training Research Programs Office.
Authoring Institution: Educational Testing Service, Princeton, NJ.