Considers the degree of bias in testlet-based alpha (internal consistency reliability) through hypothetical examples and real test data from four tests of the Iowa Tests of Basic Skills. Presents a simple formula for computing a testlet-based congeneric coefficient. (SLD)

Classically parallel, tau-equivalently parallel, and congenerically parallel models representing various degrees of part-test parallelism and their appropriateness for tests composed of multiple item formats are discussed. An appropriate reliability estimate for a test with multiple item formats is presented and illustrated. (SLD)

The calculations of D. Schretlen, R. H. B. Benedict, and J. H. Bobholz for the reliabilities of a short form of the Wechsler Adult Intelligence Scale--Revised (WAIS-R) (1994) consistently overestimated the values. More accurate values are provided for the WAIS--R and a seven-subtest short form. (SLD)

The basic equations of item response theory provide a foundation for inferring examinees' abilities and items' operating characteristics from observed responses. In practice, though, examinees will usually not have provided a response to every available item--for reasons that may or may not have been intended by the test administrator, and that…

This study provides information about the total and component scores of the Test of English as a Foreign Language (TOEFL). First, the study provides comparative global and component estimates of test-retest, alternate-form, and internal-consistency reliability, controlling for sources of measurement error inherent in the examinees and the testing…

This study examined performance of a simulated computerized adaptive test that was designed to help direct the development of a medical recertification examination. The item pool consisted of 229 single-best-answer items from a random sample of 3,000 examinees, calibrated using the two-parameter logistic model. Examinees' responses were known. For…