KR-21 reliability and its extension (coefficient [alpha]) gives the reliability estimate of test scores under the assumption of tau-equivalent forms. KR-21 reliability gives the reliability estimate for summed scores for dichotomous items when items are randomly sampled from an infinite pool of similar items (randomly parallel forms). The article…

Recommendations are made for the appropriate use and identification of traditional Kuder-Richardson formulas for the estimation of reliability. "Alpha" should be used for reliabilities estimated for tests or scales composed of items yielding scores distributed on more than two points. (SLD)

Four recent indices emphasizing the interrelationships of score distribution shape, modality, mean, and variance were investigated to determine the reliability of mastery tests. Attention was focused on the values of the indices when the cutoff score was near to or far from the modes of distribution. Five types of score distributions were…

This paper discusses the basic theory underlying confidence limits and presents reasons why psychologists should incorporate confidence ranges in their psychodiagnostic reports. Four methods for establishing confidence limits are compared. Three of the methods involve estimated true scores, and the fourth is the standard error of measurement…

Reliability coefficients of linear combinations of observed scores have anomalous properties which have led to difficulties in the investigation of difference scores and gain scores in test theory. Discrepancies between classical results and correct results obtained from more general formulas, which allow for correlated errors, are examined…

Appropriateness indexes (statistical formulas) for detecting suspiciously high or low scores on aptitude tests were presented, based on a simulation of the Scholastic Aptitude Test (SAT) with 3,000 simulated scores--2,800 normal and 200 suspicious. The traditional index--marginal probability--uses a model for the normal examinee's test-taking…