Is More Better? Combining Actuarial Risk Scales to Predict Recidivism Among Adult Sex Offenders.

The present study was conducted to determine whether combining the results of multiple actuarial risk scales increases accuracy in predicting sex offender recidivism. Multiple methods of combining 4 validated actuarial risk scales--the Violence Risk Appraisal Guide, the Sex Offender Risk Appraisal Guide, the Rapid Risk Assessment for Sexual Offense Recidivism, and the Static-99--were evaluated in a sample of 215 adult male sex offenders. These included the intuitively appealing believe-the-negative and believe-the-positive rules, adapted from medical decision making; the combination of absolute decision thresholds across a range of cutoff scores; and the statistical optimization methods of logistic regression and principal components analyses. No combination method provided a statistically significant or consistent advantage over the predictive accuracy of the single best actuarial scale.