## Answers

Average customer calls per hour on weekday mornings = 18 calls per hour

Let X be the number of customer calls per hour

X follows a Poisson distribution with λ = 18

The pdf of the Poisson distribution is

That is

x = 0, 1, 2, ….....

To find P(they get 15 or more calls an hour)

that is to find P(X ≥ 15)

P(X ≥ 15) = 1 - P(X < 15)

= 1 - P(X ≤ 14)

We use Excel function POISSON.DIST to find the probability

P(X ≥ 15) = 1- POISSON.DIST(14, 18, TRUE)

= 1 - 0.2081

= 0.7919

Answer :