Insight Psychometrics Technical Manual - Canadian Test Centre

Figure 19: Differential item functioning in the final development items in Gc,Gv, and Gf.Differential item functionning−10 −5 0 5 10Gc 1 Gc 2 Gc 3 Gv 1 Gv 2 Gv 3 Gf 1 Gf 2 Gf 3Scale and levelConcurrent validityFor subsamples of examinees in the initial development sample of Insight,information was also obtained for the WISC IV test (N=75) and for theWoodcock- Johnson III Tests of Cognitive Abilities (N=72). In Figure 20 acomparison is made of the most general scores: the Woodcock-Johnson IIIGeneral Intellectual Ability, the WISC IV Full Score, and the Insight AbilityScore (IAS) from Insight. More detailed analysis with these small subsamplesdid not seem to be warranted. Generally, the correlation of Insight IAS andWISC IV Full Score is very high (r=.88), practically at the limit of what canbe expected given the measurement errors in the two tests. The correlationwith Woodcock-Johnson III is lower (r=.62) and, from the scatterplot, it seemsthat there is some difference in the scaling and that some part of thesubsample is not following the trend line. This requires further data forinvestigation, but given the high correlation of Insight and WISC IV, it mightbe useful to have data that has all three scores on the same sample ofexaminees.19