01945nas a2200169   4500008004100000245011100041210007100152300001200223490000700235520133200242100001301574700001601587700001201603700001001615700001601625856013401641       2001                        eng d00aA comparative study of on line pretest item—Calibration/scaling methods in computerized adaptive testing0 acomparative study of on line pretest item—Calibrationscaling met  a191-2120 v383 aThe purpose of this study was to compare and evaluate five on-line pretest item-calibration/scaling methods in computerized adaptive testing (CAT): marginal maximum likelihood estimate with one EM cycle (OEM), marginal maximum likelihood estimate with multiple EM cycles (MEM), Stocking's Method A, Stocking's Method B, and BILOG/Prior. The five methods were evaluated in terms ofitem-parameter recovery, using three different sample sizes (300, 1000 and 3000). The MEM method appeared to be the best choice among these, because it produced the smallest parameter-estimation errors for all sample size conditions. MEM and OEM are mathematically similar, although the OEM method produced larger errors. MEM also was preferable to OEM, unless the amount of timeinvolved in iterative computation is a concern. Stocking's Method B also worked very well, but it required anchor items that either would increase test lengths or require larger sample sizes depending on test administration design. Until more appropriate ways of handling sparse data are devised, the BILOG/Prior method may not be a reasonable choice for small sample sizes. Stocking's Method A hadthe largest weighted total error, as well as a theoretical weakness (i.e., treating estimated ability as true ability); thus, there appeared to be little reason to use it1 aBan, J C1 aHanson, B A1 aWang, T1 aYi, Q1 aHarris, D J  uhttp://www.iacat.org/content/comparative-study-line-pretest-item%E2%80%94calibrationscaling-methods-computerized-adaptive-testing