I recently decided to revisit a 2014 case that regular readers might remember.
Back in 2014, I posted about a terrible piece of statistical 'spin' that somehow made it into the peer-reviewed Journal of Psychiatric Research. The offending authors, led by Swedish psychiatrist Lars H. Thorell, had run a study to determine whether an electrodermal hyporeactivity test was able to predict suicide and suicidal behaviour in depressed inpatients. Now, the standard way to evaluate the performance of a predictive test is with the two metrics sensitivity and specificity. Each of these can range from 0 to 1 (alternatively written as 0 to 100%), but on their own, neither of them means much: you have to consider them together. For a test which is completely uninformative (like flipping a proverbial coin), sensitivity + specificity will total 1 (100%). For a perfect test, they'll total 2 (200%). Any introductory stats textbook will ...
