As a thought experiment, if you infected an entire city with the flu, the ones to show up at the hospital are the worst cases, and if you just built your data from those people, you'd get a really really skewed perspective.
As a thought experiment, if you infected an entire city with the flu, the ones to show up at the hospital are the worst cases, and if you just built your data from those people, you'd get a really really skewed perspective.