HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Lang, T. Search for Related Content PubMed PubMed Citation Articles by Lang, T.

COMMENTARY

The need for accurate statistical reporting. A commentary on "Guidelines for reporting statistics in journals published by the American Physiological Society: the sequel"

Tom Lang Communications and Training, Davis, California

Address for reprint requests and other correspondence: T. Lang, 1925 Donner Ave., No. 3, Davis, CA 95618 (e-mail: tomlangcom{at}aol.com)

I THINK IT OBVIOUS that authors should be required to report their statistical analyses accurately and completely and that the standard error of the mean (SEM) should not be used when other statistics are more appropriate. To argue otherwise is to promote a lower standard of research. Although an outsider to your field, I have been asked to participate in this debate, so I will do so, first by addressing the misuse of SEM and then the need to require good reporting practices.

In the 1990s, I completed a systematic review of the studies identifying statistical reporting errors in biomedical journals. The results are published as a comprehensive collection of statistical reporting guidelines (1). The third most commonly mentioned error in these studies was inappropriately reporting the SEM, by using it as a descriptive statistic instead of the standard deviation (SD) or as an inferential statistic instead of the 95% confidence interval. (The two most commonly mentioned errors were confusing statistical significance with clinical importance and describing the dispersion of skewed data with the standard deviation.)

By definition, the SEM is about a 68% confidence interval, that is, it is a measure of precision for an estimated characteristic or treatment effect. It is simply wrong to use it as a measure of dispersion for a set of measurements. In this case, the SD is preferred if the data are approximately normally distributed, and the range or interpercentile range is preferred if they are not. As a measure of precision for an estimate (in clinical medicine at least) a 68% confidence interval is too close for comfort to the 50% confidence interval (which will not contain the true population value in half of similar estimates for the same population), so the more conservative 95% confidence interval is preferred.

When the SEM is used incorrectly as a measure of dispersion for a set of measurements, readers may well assume that the measurements have less variability than they actually do: the SEM is always smaller than the SD. (Indeed, an often-cited explanation for this inappropriate use of the SEM in the literature is specifically to make measurements appear to be more precise than they really are.) When the SEM is used correctly, as a 68% confidence interval, estimates are reported with less precision, which, in turn, means less confidence in subsequent inferences.

Meeting high standards should be required in all research and publication efforts, not merely recommended. We require investigators to use the scientific method; we do not just recommend that they do. We require investigators to explain their experimental procedures; we do not just recommend that they do. We even require investigators to format their references correctly; we do not just recommend that they do. Authors should be required to report statistics as completely and as accurately as every other aspect of the research. To allow ignorance, tradition, personal preference, or the practices of other journals to justify anything less is to legitimize the very forces that science attempts to overcome.

Publication is the final stage of research and in many ways, it is the most important part: it is the beginning of the formal debate about the research, the most widely distributed announcement of the research, and usually the only lasting record of the research. Why, then, should we expect less of authors at this stage of research than we do in the others?

REFERENCE

1. Lang T, Secic M. How to Report Statistics in Medicine: Annotated Guidelines for Authors, Editors, and Reviewers (2nd ed.). Philadelphia, PA: American College of Physicians, 2006.

This article has been cited by other articles:

				B. Kay The ongoing discussion regarding standard deviation and standard error Advan Physiol Educ, December 1, 2008; 32(4): 334 - 334. [Full Text] [PDF]

				D. Curran-Everett and D. J. Benos Reply to B. Kay Advan Physiol Educ, December 1, 2008; 32(4): 335 - 335. [Full Text] [PDF]

This Article Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Lang, T. Search for Related Content PubMed PubMed Citation Articles by Lang, T.