The authors present a didactic illustration of how item response theory (IRT) can be used to separate measurement bias from true group differences on homogeneous and heterogeneous scales. Several bias detection methods are illustrated with 12 unidimensional Minnesota Multiphasic Personality Inventory (MMPI) factor scales (Waller, 1999) and the 13 multidimensional MMPI validity and clinical scales. The article begins with a brief review of MMPI bias research and nontechnical reviews of the 2-parameter logistic model (2-PLM) and several IRT-based methods for bias detection. A goal of this article is to demonstrate that homogeneous and heterogeneous scales that are composed of biased items do not necessarily yield biased test scores. To that end, the authors perform differential item- and test-functioning analyses on the MMPI factor, validity, and clinical scales using data from 511 Blacks and 1,277 Whites from the California Youth Authority.

T. E. Moffitt's (1993a) hypothesis that adolescent-limited criminal offenders will have higher scores on tests of cognitive ability than life-course-persistent offenders was tested with 12 tests of cognitive ability given to a large and diverse sample of delinquent juveniles whose arrest records were collected over 20 years. This is the first investigation to empirically evaluate this proposal with longitudinal data obtained from a sample for a long enough time to distinguish life course patterns of crime. This study provided only partial support for Moffitt's hypothesis because the results varied by ethnicity. We found relatively consistent support for the hypothesis for Caucasians and Hispanics but no support for the hypothesis for African Americans. These findings are interpreted in terms of differences in developmental contexts for individual ethnic groups.

In this study, we evaluated a model of criminal offending that included the influences of family environment, cognitive ability, and early behavior problems. Analyses were conducted on a large sample of juvenile offenders (N = 4,146) who were committed to the California Youth Authority (CYA) in 1964 and 1965, with a 20-year follow-up of arrest data. Results suggest that an adverse family environment was related to the timing and frequency of juvenile delinquency. Cognitive ability, early involvement with alcohol, early age at first arrest, and the number of early arrests were all significant predictors of chronic criminal offending after ages 21, 25, and even after age 31. The timing of first arrest was found to be one of the most important variables for the prediction of chronic criminal activity.

The prediction of violence in offender populations has long been a dream of correctional decision-makers. The possibility of identifying those individuals who will engage in violent behavior in the future offers the prospect of treatment interventions to reduce such violence. Using elaborate case histories, current measures of mental and emotional functioning, and professional prognoses for a sample of 4,146 California Youth Authority wards, the present study sought to develop a classification device for estimating assaultive potential with sufficient accuracy to be useful in correctional program decisions. Simple classification procedures and multivariate approaches failed to yield an operationally practical prediction instrument that would warrant implementation in actual preventive or correctional practice. Much of the violent behavior we would wish to predict will probably never come to our attention and the part that does will be far from a representative sample. The prediction equations themselves contain the seed of self-fulfilling prophecy.~ ~*