Chapter 5 - Discrete Probability Distributions - 5-4 Other Types of Distributions - Exercises 5-4 - Page 298: 9

a. $0.018$ b. $0.073$ c. $0.147$ d. $0.762$

$p=1/20000,n=80000,\mu=np=4$ use Poisson formula a. 0 robberies $P(X=0)=\frac{4^0e^{-4}}{0!}=0.018$ b. 1 robbery $P(X=1)=\frac{4^1e^{-4}}{1!}=0.073$ c. 2 robberies $P(X=2)=\frac{4^2e^{-4}}{2!}=0.147$ d. 3 or more robberies $P(X\geq3)=1-P(0)-P(1)-P(2)=0.762$