A series of resampling studies investigated the accuracy of equating by four different methods in a random groups equating design with samples of 400, 200, 100, and 50 test takers taking each form. Six pairs of forms were constructed. Each pair was constructed by assigning items from an existing test taken by 9,000 or more test takers. The…

Operational testing programs employing item response theory (IRT) applications benefit from of the property of item parameter invariance whereby item parameter estimates obtained from one sample can be applied to other samples (when the underlying assumptions are satisfied). In theory, this feature allows for applications such as computer-adaptive…

This paper is concerned with statistical issues in differential item functioning (DIF). Four subsets of large scale performance assessment data from the Georgia Kindergarten Assessment Program-Revised (N=105,731; N=10,000; N=1,00; and N=100) were analyzed using three DIF detection methods for polytomous items to examine the congruence among the…

The purposes of this study were to introduce the iterative purification procedure and to compare this with the two-step purification procedure, to compare false positive error rates and the power of five observed score approaches and to identify factors affecting power and false positive rates in each method. This study used 2,400 data sets that…

Two aspects of criterion referenced testing are discussed: cutting scores and test length. Several practices in determining passing scores are enumerated: (1) setting passing scores so that a predetermined percent of students pass; (2) inspecting each test item to determine how important it is that it be answered correctly; (3) determining the…

The stability of Rasch test item difficulty parameters was investigated under varying conditions. Data were taken from a mathematics achievement test administered to over 2,000 Australian students. The experiments included: (1) relative stability of the Rasch, traditional, and z-item difficulty parameters using different sample sizes and designs;…