“…Because these reviews lack meta-analysis of quantitative data, it is not yet known how these instruments perform on average. Furthermore, some primary studies report very low predictive accuracies (see, for instance, Barber et al, 2008;Ondersma, Chaffin, Mullins, & LeBreton, 2005), whereas others report far better predictive accuracies (see, for instance, Loman & Siegel, 2004;De Ruiter, Hildebrand, & Van der Hoorn, 2012). Given this rather wide range, synthesizing data in a quantitative manner is essential to get insight in the overall predictive accuracy of risk assessment instruments.…”