Baker, Frank B.2011-03-162011-03-161983Baker, Frank B. (1983). Comparison of ability metrics obtained under two latent trait theory procedures. Applied Psychological Measurement, 7, 97-110. doi:10.1177/014662168300700112doi:10.1177/014662168300700112https://hdl.handle.net/11299/101631Both the BICAL and LOGIST computer programs implement a maximum likelihood procedure for jointly estimating the item and ability parameters. The two programs differ, however, with respect to (1) the anchoring procedures used to overcome the metric indeterminancy of the paradigm; (2) the item characteristic curve models employed; and (3) how the examinees are grouped within the estimation process. Three simulated sets of item response data based upon a known underlying ability metric were used to investigate the metric recovery capabilities of the two computer programs. The results showed that both programs recovered a transformation of the underlying metric via a common equation, but the elements used in this equation were program specific. The transformation of the metric yielded by BICAL to the underlying metric depended only upon the item characteristic curve parameters, whereas the LOGIST transformation also depended upon the frequency distribution of the estimated ability scores over the underlying ability metric. The empirical results indicate that both transformations are quite sensitive to errors in the average value of the obtained item discrimination indices. Because LOGIST groups examinees by ability levels and BICAL does so by raw score levels, the variability of the transformed ability estimates yielded by BICAL were smaller than those from LOGIST. The results suggest that when comparing results yielded by the two computer programs, particular attention should be paid to the characteristics of the obtained metrics.enArticle