01712nas a2200169   4500008004100000245015800041210006900199300001000268490000700278520105400285100001901339700001801358700001601376700001201392700001601404856012201420       2003                        eng d00aSmall sample estimation in dichotomous item response models: Effect of priors based on judgmental information on the accuracy of item parameter estimates0 aSmall sample estimation in dichotomous item response models Effe  a27-510 v273 aLarge item banks with properly calibrated test items are essential for ensuring the validity of computer-based tests. At the same time, item calibrations with small samples are desirable to minimize the amount of pretesting and limit item exposure. Bayesian estimation procedures show considerable promise with small examinee samples. The purposes of the study were (a) to examine how prior information for Bayesian item parameter estimation can be specified and (b) to investigate the relationship between sample size and the specification of prior information on the accuracy of item parameter estimates. The results of the simulation study were clear: Estimation of item response theory (IRT) model item parameters can be improved considerably. Improvements in the one-parameter model were modest; considerable improvements with the two- and three-parameter models were observed. Both the study of different forms of priors and ways to improve the judgmental data used in forming the priors appear to be promising directions for future research. 1 aSwaminathan, H1 aHambleton, RK1 aSireci, S G1 aXing, D1 aRizavi, S M  uhttp://mail.iacat.org/content/small-sample-estimation-dichotomous-item-response-models-effect-priors-based-judgmental02778nas a2200133   4500008004100000245009800041210006900139300000900208490000700217520225500224653003402479100001602513856011502529       2002                        eng d00aThe effect of test characteristics on aberrant response patterns in computer adaptive testing0 aeffect of test characteristics on aberrant response patterns in   a33630 v623 aThe advantages that computer adaptive testing offers over linear tests have been well documented. The Computer Adaptive Test (CAT) design is more efficient than the Linear test design as fewer items are needed to estimate an examinee's proficiency to a desired level of precision. In the ideal situation, a CAT will result in examinees answering different number of items according to the stopping rule employed. Unfortunately, the realities of testing conditions have necessitated the imposition of time and minimum test length limits on CATs. Such constraints might place a burden on the CAT test taker resulting in aberrant response behaviors by some examinees. Occurrence of such response patterns results in inaccurate estimation of examinee proficiency levels. This study examined the effects of test lengths, time limits and the interaction of these factors with the examinee proficiency levels on the occurrence of aberrant response patterns. The focus of the study was on the aberrant behaviors caused by rushed guessing due to restrictive time limits. Four different testing scenarios were examined; fixed length performance tests with and without content constraints, fixed length mastery tests and variable length mastery tests without content constraints. For each of these testing scenarios, the effect of two test lengths, five different timing conditions and the interaction between these factors with three ability levels on ability estimation were examined. For fixed and variable length mastery tests, decision accuracy was also looked at in addition to the estimation accuracy. Several indices were used to evaluate the estimation and decision accuracy for different testing conditions. The results showed that changing time limits had a significant impact on the occurrence of aberrant response patterns conditional on ability. Increasing test length had negligible if not negative effect on ability estimation when rushed guessing occured. In case of performance testing high ability examinees while in classification testing middle ability examinees suffered the most. The decision accuracy was considerably affected in case of variable length classification tests. (PsycINFO Database Record (c) 2003 APA, all rights reserved).10acomputerized adaptive testing1 aRizavi, S M  uhttp://mail.iacat.org/content/effect-test-characteristics-aberrant-response-patterns-computer-adaptive-testing