https://en.wikipedia.org/wiki/Reliability_of_Wikipedia#Comparative_studies
In December 2005, the journal Nature conducted a single-blind study comparing the accuracy of a sample of articles from Wikipedia and Encyclopædia Britannica. The sample included 42 articles on scientific topics, including biographies of well-known scientists. The articles were compared for accuracy by academic reviewers who remained anonymous − a customary practice for journal article reviews. Based on their review, the average Wikipedia article contained 4 errors or omissions; the average Britannica article, 3. Only 4 serious errors were found in Wikipedia, and 4 in Encyclopædia Britannica. The study concluded: "Wikipedia comes close to Britannica in terms of the accuracy of its science entries",[2] although Wikipedia's articles were often "poorly structured".[2]
Encyclopædia Britannica expressed concerns, leading Nature to release further documentation of its survey method.[28] Based on this additional information, Encyclopædia Britannica denied the validity of the Nature study, stating that it was "fatally flawed". Among Britannica's criticisms were that excerpts rather than the full texts of some of their articles were used, that some of the extracts were compilations that included articles written for the youth version, that Nature did not check the factual assertions of its reviewers, and that many points which the reviewers labeled as errors were differences of editorial opinion.[29] Nature acknowledged the compiled nature of some of the Britannica extracts, but denied that this invalidated the conclusions of the study.[30] Encyclopædia Britannica also argued that while the Nature study showed that the error rate between the two encyclopedias was similar, a breakdown of the errors indicated that the mistakes in Wikipedia were more often the inclusion of incorrect facts, while the mistakes in Britannica were "errors of omission", making "Britannica far more accurate than Wikipedia, according to the figures".[29] Nature has since rejected the Britannica response,[31] stating that any errors on the part of its reviewers were not biased in favor of either encyclopedia, that in some cases it used excerpts of articles from both encyclopedias, and that Britannica did not share particular concerns with Nature before publishing its "open letter" rebuttal.[32][33]
In June 2006, Roy Rosenzweig, a professor specializing in American history, published a comparison of the Wikipedia biographies of 25 Americans to the corresponding biographies found on Encarta and American National Biography Online. He wrote that Wikipedia is "surprisingly accurate in reporting names, dates, and events in U.S. history" and described some of the errors as "widely held but inaccurate beliefs". However, he stated that Wikipedia often fails to distinguish important from trivial details, and does not provide the best references. He also complained about Wikipedia's lack of "persuasive analysis and interpretations, and clear and engaging prose".[34] Wikipedia's policies on original research, including unpublished synthesis of published data, disallow new analysis and interpretation not found in reliable sources.
A web-based survey conducted from December 2005 to May 2006 by Larry Press, a professor of Information Systems at California State University at Dominguez Hills, assessed the "accuracy and completeness of Wikipedia articles".[35] Fifty people accepted an invitation to assess an article. Of the fifty, seventy-six percent (76%) agreed or strongly agreed that the Wikipedia article was accurate, and forty-six percent (46%) agreed or strongly agreed that it was complete. Eighteen people compared the article they reviewed to the article on the same topic in the Encyclopædia Britannica. Opinions on accuracy were almost equal between the two encyclopedias (6 favoring Britannica, 7 favoring Wikipedia, 5 stating they were equal), and eleven of the eighteen (61%) found Wikipedia somewhat or substantially more complete, compared to seven of the eighteen (39%) for Britannica. The survey did not attempt random selection of the participants, and it is not clear how the participants were invited.[36]
The German computing magazine c't performed a comparison of Brockhaus Multimedial, Microsoft Encarta, and the German Wikipedia in October 2004: Experts evaluated 66 articles in various fields. In overall score, Wikipedia was rated 3.6 out of 5 points (B-).[37] A second test by c't in February 2007 used 150 search terms, of which 56 were closely evaluated, to compare four digital encyclopedias: Bertelsmann Enzyklopädie 2007, Brockhaus Multimedial premium 2007, Encarta 2007 Enzyklopädie and Wikipedia. It concluded: "We did not find more errors in the texts of the free encyclopedia than in those of its commercial competitors."[38]
Viewing Wikipedia as fitting the economists' definition of a perfectly competitive marketplace of ideas, George Bragues (University of Guelph-Humber), examined Wikipedia's articles on seven top Western philosophers: Aristotle, Plato, Immanuel Kant, René Descartes, Georg Wilhelm Friedrich Hegel, Thomas Aquinas, and John Locke. Wikipedia's articles were compared to a consensus list of themes culled from four reference works in philosophy. Bragues found that, on average, Wikipedia's articles only covered 52% of consensus themes. No errors were found, though there were significant omissions.[39]
PC Pro magazine (August 2007) asked experts to compare four articles (a small sample) in their scientific fields between Wikipedia, Britannica and Encarta. In each case Wikipedia was described as "largely sound", "well handled", "performs well", "good for the bare facts" and "broadly accurate." One article had "a marked deterioration towards the end" while another had "clearer and more elegant" writing, a third was assessed as less well written but better detailed than its competitors, and a fourth was "of more benefit to the serious student than its Encarta or Britannica equivalents." No serious errors were noted in Wikipedia articles, whereas serious errors were noted in one Encarta and one Britannica article.[40]
In October 2007, Australian magazine PC Authority published a feature article on the accuracy of Wikipedia. The article compared Wikipedia's content to other popular online encyclopedias, namely Britannica and Encarta. The magazine asked experts to evaluate articles pertaining to their field. Wikipedia was comparable to the other encyclopedias, topping the chemistry category.[41]
In December 2007, German magazine Stern published the results of a comparison between the German Wikipedia and the online version of the 15-volume edition of Brockhaus Enzyklopädie. The test was commissioned to a research institute (Cologne-based WIND GmbH), whose analysts assessed 50 articles from each encyclopedia (covering politics, business, sports, science, culture, entertainment, geography, medicine, history and religion) on four criteria (accuracy, completeness, timeliness and clarity), and judged Wikipedia articles to be more accurate on the average (1.6 on a scale from 1 to 6, versus 2.3 for Brockhaus with 1 as the best and 6 as the worst). Wikipedia's coverage was also found to be more complete and up to date; however, Brockhaus was judged to be more clearly written, while several Wikipedia articles were criticized as being too complicated for non-experts, and many as too lengthy.[42][43][44]
In its April 2008 issue British computing magazine PC Plus compared the English Wikipedia with the DVD editions of World Book Encyclopedia and Encyclopædia Britannica, assessing for each the coverage of a series of random subjects. It concluded The quality of content is good in all three cases and advised Wikipedia users Be aware that erroneous edits do occur, and check anything that seems outlandish with a second source. But the vast majority of Wikipedia is filled with valuable and accurate information.[45]
Reavley et al. (2012) compared the quality of articles on select mental health topics on Wikipedia with corresponding articles in Encyclopaedia Britannica and a psychiatry textbook. They asked experts to rate article content with regard to accuracy, up-to-dateness, breadth of coverage, referencing and readability. Wikipedia scored highest on all criteria except readability, and the authors concluded that Wikipedia is as good as or better than Britannica and a standard textbook.[9]
Expert opi