Hinkle Joshua C, Weisburd David, Famega Christine, Ready Justin
Department of Criminal Justice and Criminology, Georgia State University, Atlanta, GA, USA.
Eval Rev. 2013 Jun-Aug;37(3-4):213-38. doi: 10.1177/0193841X13519799. Epub 2014 Feb 11.
Hot spots policing is one of the most influential police innovations, with a strong body of experimental research showing it to be effective in reducing crime and disorder. However, most studies have been conducted in major cities, and we thus know little about whether it is effective in smaller cities, which account for a majority of police agencies. The lack of experimental studies in smaller cities is likely in part due to challenges designing statistically powerful tests in such contexts.
The current article explores the challenges of statistical power and "noise" resulting from low base rates of crime in smaller cities and provides suggestions for future evaluations to overcome these limitations.
Data from a randomized experimental evaluation of broken windows policing in hot spots are used to illustrate the challenges that low base rates present for evaluating hot spots policing programs in smaller cities.
Analyses show low base rates make it difficult to detect treatment effects. Very large effect sizes would be required to reach sufficient power, and random fluctuations around low base rates make detecting treatment effects difficult, irrespective of power, by masking differences between treatment and control groups.
Low base rates present strong challenges to researchers attempting to evaluate hot spots policing in smaller cities. As such, base rates must be taken directly into account when designing experimental evaluations. The article offers suggestions for researchers attempting to expand the examination of hot spots policing and other microplace-based interventions to smaller jurisdictions.
热点警务是最具影响力的警务创新之一，大量实证研究表明其在减少犯罪和混乱方面是有效的。然而，大多数研究是在大城市进行的，因此我们对其在占警察机构多数的小城市是否有效知之甚少。小城市缺乏实证研究，部分原因可能是在此类背景下设计具有统计效力的测试存在挑战。
本文探讨了小城市犯罪低发率导致的统计效力和“噪音”挑战，并为未来评估提供克服这些限制的建议。
来自热点地区破窗警务随机实验评估的数据用于说明低发案率对评估小城市热点警务项目带来的挑战。
分析表明，低发案率使得难以检测到处理效果。需要非常大的效应量才能达到足够的效力，并且低发案率周围的随机波动会掩盖处理组与对照组之间的差异，从而无论效力如何都难以检测到处理效果。
低发案率给试图评估小城市热点警务的研究人员带来了巨大挑战。因此，在设计实验评估时必须直接考虑发案率。本文为试图将热点警务及其他基于微观场所的干预措施的研究扩展到较小辖区的研究人员提供了建议。
