  Increasing integration and availability of data on large groups of persons
has been accompanied by proliferation of statistical and other algorithmic
prediction tools in banking, insurance, marketiNg, medicine, and other FIelds
(see e.g., Steyerberg (2009a;b)). Controversy may ensue when such tools are
introduced to fields traditionally reliant on individual clinical evaluations.
Such controversy has arisen about "actuarial" assessments of violence
recidivism risk, i.e., the probability that someone found to have committed a
violent act will commit another during a specified period. Recently Hart et al.
(2007a) and subsequent papers from these authors in several reputable journals
have claimed to demonstrate that statistical assessments of such risks are
inherently too imprecise to be useful, using arguments that would seem to apply
to statistical risk prediction quite broadly. This commentary examines these
arguments from a technical statistical perspective, and finds them seriously
mistaken in many particulars. They should play no role in reasoned discussions
of violence recidivism risk assessment.
