Question

A call-in customer service center knows they get on average 18 calls per hour on weekday mornings. What is the probability they get 15 or more calls an hour? O 1) .9345 O2).2867 03) 7919 O4).0415

Answer 1

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                   

e-@* P(X = x) =

That is                   

e-18 (18)* P(X = x) = x!
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 :                  
$\mathbf{\circ \ \ \ 3)\ \ .7919 }$