How big until covid? (Solution)

Let’s assume that each person has a 2% chance of having COVID and each person’s probability is independent of one another’s.

We can set up an equation. If the number of people attending the party is \(N\), then the probability that none of them have COVID is \(0.98^N\). So the probability that someone does have COVID is \(1 - 0.98^N\).

\[\begin{align*} 1 - 0.98 ^ N &= 0.5 \\ 0.5 &= 0.98 ^ N \\ \frac{log(0.5)}{log(0.98)} &= N \\ 34.3 &\approx N \end{align*}\]

So, you can invite 34 people to your party and still have less than a 50% chance that COVID is also attending!