A Look at the Difficulty and Predictive Validity of LS/CMI Items With Rasch Modeling

Abstract

The current study aimed to provide data on the performance of items, dimensions, and the total score of the Level of Service/Case Management Inventory (LS/CMI), one of the most internationally used actuarial scales for the prediction of general recidivism in convicted persons. Using the full population of Quebec’s male incarcerated population evaluated between 2008 and 2015 with a 2-year follow-up ( N = 15,961), results indicated that the predictive validity of the scale and its components was in line or better than effect sizes reported in other validation studies. A Rasch model was computed to obtain the difficulty parameter of LS/CMI items. Results indicated that items had varying levels of difficulty and covered the whole spectrum of the risk continuum. However, difficulty in Rasch was uncorrelated with the predictive validity of items, which casts a doubt on the applicability of some aspects of item response theory to actuarial scales.