$X$ follows a Poisson distribution with $\lambda = 1$. What is $P(X = 3)$? (Take $e^{-1} = 0.3679$.)

Explanation

1. 01

   $P(X = r) = \frac{e^{-\lambda}\lambda^{r}}{r!}$ with $\lambda = 1$, $r = 3$.

2. 02

   $= \frac{0.3679 \times 1^{3}}{3!} = \frac{3679}{60000}$.