On average the number of people who go through the checkout

On average, the number of people who go through the check-out at a local grocery store is 8 people per hour. In a randomly selected hour, find the probability that no more than 2 people go through the check-out.

a) 0.0161

b) 0.0996

c) 0.0620

d) 0.0138

Solution

Possion Distribution
PMF of P.D is = f ( k ) = e- x / x!
Where   
= parameter of the distribution.
x = is the number of independent trials
P( X < = 2) = P(X=2) + P(X=1) + P(X=0)
= e^-8 * 8 ^ 2 / 2! + e^-8 * 2 ^ 1 / 1! + e^-8 * ^ 0 / 0!
= 0.0138