Pop Quiz. Let's say you take a Covid-19 antibody test. The test has an accuracy of 90%. To be more specific, both its sensitivity (the proportion of actual positives that are correctly identified as such) and specificity (the proportion of actual negatives that are correctly identified as such) are 90%. The test comes back positive. … Continue reading Base Rate Fallacy

Whenever you do a math calculation, it's a good idea to do a sanity check. The goal is to do a quick test to determine whether the answer could possibly be true. Not that it is true, but that it could be true. Or, to put it another way, to verify that it isn't obviously … Continue reading Sanity Check

I haven't written about Covid-19, because lots of very smart people are already doing great analysis of it. (Of course, there's also been a lot of crappy analysis too, usually by someone with a political ax to grind). But... One thing that struck me recently, is that we're about to embark on a large multiple … Continue reading A Grand Experiment