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T.A. Lang & D.G. Altman: Introducing the SAMPL guidelines

20/03/2013

Basic Statistical Reporting for Articles Published in Biomedical Journals: The “Statistical Analyses and Methods in the Published Literature” or “The SAMPL Guidelines”

Thomas A. Lang and Douglas G. Altman.

 

“Have they reflected that the sciences founded on observation can only be promoted by statistics? . . . If medicine had not neglected this instrument, this means of progress, it would possess a greater number of positive truths, and  stand less liable to the accusation of being a science of unfixed principles, vague and conjectural.”

Jean-Etienne Dominique Esquirol, an early French psychiatrist, quoted in The Lancet, 1838 [1]

Tom Lang

Introduction

The first major study of the quality of statistical reporting in the biomedical literature was published in 1966 [2]. Since then, dozens of similar studies have been published, every one of which has found that large proportions of articles contain errors in the application, analysis, interpretation, or reporting of statistics or in the design or conduct of research. (See, for example, references 3 through 19.) Further, large proportions of these errors are serious enough to call the authors’ conclusions into question [5,18,19]. The problem is made worse by the fact that most of these studies are of the world’s leading peer-reviewed general medical and specialty journals.

Although errors have been found in more complex statistical procedures [20,21,22], paradoxically, many errors are in basic, not advanced, statistical methods [23]. Perhaps advanced methods are suggested by consulting statisticians, who then competently perform the analyses, but it is also true that authors are far more likely to use only elementary statistical methods, if they use any at all [23-26]. Still, articles with even major errors continue to pass editorial and peer review and to be published in leading journals.

The truth is that the problem of poor statistical reporting is long-standing, widespread, potentially serious, concerns mostly basic statistics, and yet is largely unsuspected by most readers of the biomedical literature [27].

More than 30 years ago, O’Fallon and colleagues recommended that “Standards governing the content and format of statistical aspects should be developed to guide authors in the preparation of manuscripts”  [28]. Despite the fact that this call has since been echoed by several others (17,18,29-32), most journals have still not included in their Instructions for Authors more than a paragraph or two about reporting statistical methods [33].  However, given that many statistical errors concern basic statistics, a comprehensive—and comprehensible—set of reporting guidelines might improve how statistical analyses are documented.

Doug AltmanIn light of the above, we present here a set of statistical reporting guidelines suitable for medical journals to include in their Instructions for Authors. These guidelines tell authors, journal editors, and reviewers how to report basic statistical methods and results. Although these guidelines are limited to the most common statistical analyses, they are nevertheless sufficient to prevent most of the reporting deficiencies routinely found in scientific articles; they may also help to prevent some reporting errors by focusing attention on key points in the analyses.

Unlike many of other guidelines, the SAMPL guidelines were not developed by a formal consensus-building process, but they do draw considerably from published guidelines [27,34-37]. In addition, a comprehensive review of the literature on statistical reporting errors reveals near universal agreement on how to report the most common methods [27].

Statistical analyses are closely related to the design and activities of the research itself. However, our guidelines do not address the issues related to the design and conduct of research. Instead, we refer readers to the EQUATOR Network website (www.equator-network.org) where guidelines for reporting specific research designs can be found. (For example, see the CONSORT [38], TREND [39], STROBE [40]) These guidelines for reporting methodologies all include items on reporting statistics, but the guidelines presented here are more specific and complement, not duplicate, those in the methodology guidelines.

We welcome feedback and anticipate the need to update this guidance in due course.

Lang T, Altman D. Basic statistical reporting for articles published in clinical medical journals: the SAMPL Guidelines. In: Smart P, Maisonneuve H, Polderman A (eds). Science Editors’ Handbook, European Association of Science Editors, 2013. This document may be reprinted without charge but must include the original citation.

About the authors

  • Thomas A. Lang is Principal of Tom Lang Communications and Training International
  • Douglas G. Altman is Director of the Centre for Statistics in Medicine, Oxford University

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