Corona Corona (where you been so long?)

As testing for Covid-19 immunity becomes widely available, it's important to understand the "Base Rate Fallacy" that leads people who test positive to reach false conclusions about the true probability that they are actually immune.  Let's assume that 10% of the population is immune. Epidemiologists refer to this as the population's "base rate" of immunity. If the base rate is 10%, there's a 10% chance that a randomly-selected individual is immune.  Now test that individual for immunity with a test known from clinical trials to result in 5% false positives. this means that 5% of the time, individuals testing immune actually are not. Let's also assume that the test doesn't result in any false negatives, meaning that everyone who is immune will test immune.  When we use this test on our randomly selected individual and she tests positive (immune), what is now the probability that she really is immune? The answer is that a positive test changes ...

One of the lessons that USA should learn from Wave One and follow in planning for Wave Two is that it is better to furlough than to unemploy. In many European countries, government policy during Wave One has been to advise business to furlough workers rather than unemploy them. Furloughed workers keep their jobs, and continue receiving their salaries. Businesses who furlough their employees are reimbursed by government for the full cost of their workers salaries. USA's Wave One policy, by contrast, is a combination of unemployment insurance and the Payroll Protection Plan. If the USG had thought it through before Wave One happened, it would have realized that relying on the traditional system of paying benefits to unemployed workers would be a mistake, because that system is designed for workers who lose a job they don't expect to return to. Unemployment benefits sare meant to tide unemployed people over while they look for new job.   The furlough approach recognizes that the ...