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Kernel Density Bandwidth Specification in Neighborhood Violence Prevention Research.
Hiwot Y Zewdie1, Nicole Asa2,3, Ali Rowhani-Rahbar2,3
1Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA, USA. hzewdie@uw.edu.
Summary
Data-driven bandwidth selection in kernel density estimation (KDE) for place-based violence prevention can distort results. Researchers must carefully choose KDE parameters to accurately detect intervention effects on crime.
Area of Science:
- Criminology
- Geospatial Analysis
- Public Health
Background:
- Place-based interventions are used to reduce violence.
- Kernel density estimation (KDE) is a method for analyzing geospatial point data, such as crime incidents.
- The effectiveness of KDE is influenced by the bandwidth parameter, which determines the smoothing extent of the data.
Purpose of the Study:
- To quantify the variability of bandwidths selected using data-driven methods in KDE.
- To examine how different bandwidth sizes impact the estimation of simulated place-based intervention effects on violence.
Main Methods:
- Utilized violent crime data from Philadelphia (2013-2023).
- Calculated bandwidth sizes using two default data-driven criteria for crime-year combinations.
- Simulated a hypothetical intervention with a known effect and analyzed its detectability across various bandwidths using Poisson regression.
Main Results:
- Bandwidth sizes varied significantly based on the data-driven method, crime type, and year, ranging from 45.9 to 48,450 feet.
- Simulated intervention effects were only detectable within bandwidths of 200 to 2900 feet.
- Larger bandwidths led to inaccurate conclusions, suggesting the intervention was ineffective or even crime-increasing.
Conclusions:
- Data-driven bandwidth selection in KDE can obscure or distort the true effects of place-based interventions.
- Researchers must critically and transparently select KDE parameters for accurate violence prevention research.
- Appropriate bandwidth selection is crucial for reliably assessing the impact of place-based violence reduction strategies.
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