## 25 março 2020

Qual a chance que alguém que você conheça irá morrer do Covid-19?

You don’t need much to answer this question. You need an estimate of the infection fatality risk (IFR), an estimate of the proportion of the population that will become infected (infection risk, IR), and the number of people that a person knows on average. Coincidentally, in 2013 you published an article in the NYTimes on the latter. Your answer was 600 people.

So, for the remaining quantities. Recent estimates of the IFR range from 0.39 – 1.33%. Recent estimates of the IR range from 40–80%. With this information, the probability of at least one death out of n people, is simply 1 – dbinom(0, n, theta), with theta = (IFR) x (IR). Using “middle of the range” estimates for IFR and IR, we get theta = 0.00516.

This figure shows the probability that at least one person you know (meaning “you” in general) will die, as a function of the number of people you know. If you know 600 people, the probability of at least one death among people you know is greater than 95%:

Gellman acredita que o valor, de 95%, está superestimado.