From the article entitled "The reliability of Wikipedia":
The reliability of Wikipedia, compared to other encyclopedias and more specialized sources, is assessed in many ways, including statistically, by comparative review, analysis of the historical patterns, and strengths and weaknesses inherent in the editing process unique to Wikipedia.
Because Wikipedia is open to anonymous and collaborative editing, assessments of its reliability usually include examinations of how quickly false or misleading information is removed. An early study conducted by IBM researchers in 2003—two years following Wikipedia's establishment—found that "vandalism is usually repaired extremely quickly — so quickly that most users will never see its effects" and concluded that Wikipedia had "surprisingly effective self-healing capabilities".
A notable early study in the journal Nature suggested that in 2005, Wikipedia scientific articles came close to the level of accuracy in Encyclopædia Britannica and had a similar rate of "serious errors". This study was disputed by Encyclopædia Britannica.
By 2010 reviewers in medical and scientific fields such as toxicology, cancer research and drug information reviewing Wikipedia against professional and peer-reviewed sources found that Wikipedia's depth and coverage were of a very high standard, often comparable in coverage to physician databases and considerably better than well known reputable national media outlets. Wikipedia articles were cited as references in journals (614 cites in 2009) and as evidence in trademark and higher court rulings. However, omissions and readability sometimes remained an issue – the former at times due to public relations removal of adverse product information and a considerable concern for fields such as medicine.