Accuracy and prediction… the limits of our intuition

Massimiliano Sassoli de Bianchi
5 min readDec 12, 2020

Imagine that an infectious disease is spreading around the world, and that a test is available, with for example a proven accuracy of 90%. Ask yourself the following question:

What is the likelihood that I am infected, if the test is positive?

Usually, people answer that the probability is 90%, that is, equal to the accuracy of the test. But this…