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Evaluating a Sampling Frame of Private Security Firms

Keywords: frame quality, coverage, business register, matching, National Private Security Survey (NPSS)

This paper presents an approach to evaluate the quality and coverage of a frame of business establishments. Typically coverage cannot be assessed for surveys that utilize commercial databases of establishments because no gold standard list exists outside of the Census Bureau. However, this study was able to utilize a state-based list that served as a proxy gold standard. As a part of a design study for the Bureau of Justice Statistics, we developed and evaluated a frame of contract security firms for the National Private Security Survey. This frame combined lists of private security industry companies from D&B and InfoUSA into a single “superframe.” Frame quality was evaluated though the percent of establishments that were incorrectly classified as security companies and by the number of duplicate companies. Over 81% of superframe companies were unique companies and were correctly classified. Coverage of the target population was evaluated using licensing lists from 17 states that required contract security firms to be licensed. We discuss difficulties of comparing lists from multiple sources and attempts to resolve these difficulties and calculate a coverage rate.