Question

The average number of customers, who appear in a counter of a certain bank per minute is two. Find the probability that during a given minute 

(i) No customer appears 

(ii) three or more customers appear.

Answer 1

Let X denote the number of customers. 

Given λ = 2 

(i) P (no customer) = P (X = 0) 

= (e^-2(2)⁰)/ 0!

= e^-2 

= 0.1353 

(ii) P (3 or more customers) = P (X ≥ 3) 

Thus during a given minute, the probability that three or more customers appear is 0.3235.