Solution
= Solution
For a nonnegative integer $K$, add the probabilities of the disjoint events with $0,1,\ldots,K$ goals. The <cumulative distribution function> is
$$
\boxed{P(X\leq K)=e^{-\lambda}\sum_{k=0}^{K}\frac{\lambda^k}{k!}}.
$$
= Solution
For a nonnegative integer $K$, add the probabilities of the disjoint events with $0,1,\ldots,K$ goals. The <cumulative distribution function> is
$$
\boxed{P(X\leq K)=e^{-\lambda}\sum_{k=0}^{K}\frac{\lambda^k}{k!}}.
$$