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 :