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The unit of analysis error in studies about physicians’ patient care behavior

Journal of General Internal Medicine volume 7, pages 623–629 (1992)Cite this article

Abstract

Objective:To estimate the frequency with which patients are incorrectly used as the unit of analysis among statistical calculations in published studies of physicians’ patient care behavior.

Design:Retrospective review of studies published during 1980–1990.

Articles:54 articles retrieved by a computerized search using medical subject beadings for physicians and study characteristics. Article selection criteria included the requirement that the physician should have been the correct unit of analysis.

Intervention:Presence of the error was determined by consensus using published criteria.

Main results:The error was present in 38 articles (70%). The number of study physicians was reported in 35 articles (65%). The error was found in 57% of articles that reported the number of study physicians and in 95% of those that did not. The error rate was not lower among articles published more recently nor among those published in journals with higher rates of article citations in the medical literature.

Conclusion:The unit of analysis error occurs frequently and can generate artificially low p values. Failure to report the number of study physicians can be a clue that this type of error has been made.

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Author notes

  1. George W. Divine PhD

    Present address: Henry Ford Health System, Detroit, Michigan

  2. J. Trig Brown MD, MPH

    Present address: Southeast Permanente Medical Group, Durham, North Carolina

Authors and Affiliations

  1. the Department of Community and Family Medicine, Division of Biometry and Medical Informatics, Duke University, Durham, North Carolina

    George W. Divine PhD

  2. Division of Occupational and Environmental Medicine, Duke University, Durham, North Carolina

    Linda M. Frazier MD

  3. the Department of Medicine, Division of General Internal Medicine, Duke University, Durham, North Carolina

    J. Trig Brown MD, MPH

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  2. J. Trig Brown MD, MPH
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  3. Linda M. Frazier MD
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Divine, G.W., Brown, J.T. & Frazier, L.M. The unit of analysis error in studies about physicians’ patient care behavior. J Gen Intern Med 7, 623–629 (1992). https://doi.org/10.1007/BF02599201

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