Question

The number of traffic accidents per week in a small city has a mean equal to 3. What is the probability of exactly 2 accidents occurring in 2 weeks?

Answer 1

Let $X=$ the number of traffic accidents per period: $X\sim Po(\lambda t).$

Given $\lambda=3, t=2.$

$$P(X=2)=\dfrac{e^{-3(2)}(3(2))^2}{2!}\approx0.04462$$