ABSTRACT
Mental Model #14 explains how to determine causation and why causation is important for the police profession to understand. When two variables change in relationship to each other, there are four requirements for deeming the relationship causal rather than correlational—there is only one intervention, the intervention occurs before the outcome (temporal requirement), there is pre/post data, and there is a comparison group. Sherman argues the only way to determine if an intervention caused a crime reduction is to have a comparison group. In this section I give examples of what makes a good comparison group and why they are so important.
