A common method of presenting data in the police performance environment is the use of binary comparisons. This involves comparing two isolated numeric values, then interpreting the difference between them as a trajectory, or assuming it is significant. The practice is commonplace within UK police forces, appearing at face value to be a simple method for interpreting data. However, concerns exist about the efficacy of the approach; furthermore, experience suggests the practice leads to unwarranted assumptions, which impair decision-making and encourage inappropriate behavioural responses. This article outlines key findings from the author’s doctoral research, which utilizes experimental psychometric testing to assess the predictability of adverse behavioural outcomes associated with the practice.