Editing Chi-squared test (section)

== Yates's correction for continuity ==
{{Main|Yates's correction for continuity}}
Using the [[chi-squared distribution]] to interpret [[Pearson's chi-squared test|Pearson's chi-squared statistic]] requires one to assume that the [[Discrete probability distribution|discrete]] probability of observed [[binomial distribution|binomial frequencies]] in the table can be approximated by the continuous [[chi-squared distribution]]. This assumption is not quite correct and introduces some error.

To reduce the error in approximation, [[Frank Yates]] suggested a correction for continuity that adjusts the formula for [[Pearson's chi-squared test]] by subtracting 0.5 from the absolute difference between each observed value and its expected value in a {{nowrap|2 × 2}} contingency table.<ref name=Yates>{{cite journal|author-link=Frank Yates|last=Yates|first=Frank|date=1934|title=Contingency table involving small numbers and the {{math|χ<sup>2</sup>}} test|journal=Supplement to the Journal of the Royal Statistical Society|volume=1|issue=2|pages=217–235|jstor=2983604|doi=10.2307/2983604}}</ref> This reduces the chi-squared value obtained and thus increases its [[p-value|''p''-value]].