SOLUTION: A study of the checkout lines at the Safeway Supermarket in the South Strand area revealed that between 4 and 7 P.M. on weekdays there is an average of four customers waiting in li

Question 971891: A study of the checkout lines at the Safeway Supermarket in the South Strand area revealed that between 4 and 7 P.M. on weekdays there is an average of four customers waiting in line. What is the probability that you visit Safeway today during this period and find:
a. No customers are waiting?
b. Four customers are waiting?
c. Four or fewer are waiting?
d. Four or more are waiting?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
I would use a Poisson distribution: discrete, small, could theoretically be infinite, and no other information here available.
lambda=4
e(-4)=0.01832 That is the probability of 0.
probability of 4= e (-4) 4^4/4! = 0.2930 (expected value)
probability of 4 or fewer is 0.629 from table
probability of 4 or more are waiting is 0.371 (from ≥4 + 0.2930 (4 exactly)=0.664

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