If at first you succeed, try again!

One of the fundamental principles of scientific research is replication—retesting of apparently successful interventions to make sure the initial success was not a fluke. The principle is widely accepted and practiced in the physical and biological sciences, but is less so in the social sciences. Today’s case in point, a replication of the Hawaii Opportunity Probation with Enforcement (HOPE) program, makes clear why replication of positive findings is also essential in the social sciences before policymakers can be confident that a social program is truly effective.