Nat. Methods 10, 1139–1140 (2013); published online 26 November 2013; corrected after print 26 November 2013; corrected after print 3 August 2015

In the version of this article initially published, the terms “sensitivity” and “specificity” and the related descriptors “sensitive” and “specific” were mistakenly switched in three instances. The errors have been corrected in the HTML and PDF versions of the article.