Wikipedia, and 4 in Britannica. The study concluded that "Wikipedia comes close to Britannica in terms of the accuracy of its science entries", although Wikipedia's articles were often "poorly structured". Encyclopædia Britannica expressed concerns, leading Nature to release further documentation of its survey method. Based on this additional information, Encyclopædia Britannica denied the validity of the Nature study, stating that it was "fatally flawed". Among Britannicas 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 the reviewers labeled as errors were differences of editorial opinion. Britannica further stated that "While the heading proclaimed that 'Wikipedia comes close to Britannica in terms of the accuracy of its science entries,' the numbers buried deep in the body of the article said precisely the opposite: Wikipedia in fact had a third more inaccuracies than Britannica. (As we demonstrate below, 's research grossly exaggerated 's inaccuracies, so we cite this figure only to point out the slanted way in which the numbers were presented.)" Nature acknowledged the compiled nature of some of the Britannica extracts, but denied that this invalidated the conclusions of the study. Encyclopædia Britannica also argued that 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". Nature has since rejected the Britannica response, 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. The point-for-point disagreement between these two parties that addressed the compilation/text excerpting and very small sample size issues—argued to bias the outcome in favor of Wikipedia, versus a comprehensive, full article, large sample size study favoring the quality-controlled format of Britannica—have been echoed in online discussions, including of articles citing the Nature study, e.g., where a "flawed study design" for manual selection of articles/article portions, the lack of study "statistical power" in its comparing 40 articles from over 100,000 Britannica and over 1 million English