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Algebra ->  Probability-and-statistics -> SOLUTION: [The other time i [ask free tutors] without registering, so.. this q is a repeat, thank you tutors! i am really glad to stumble upon this site! really helps me a lot!] Q: A s      Log On


   



Question 971953: [The other time i [ask free tutors] without registering, so.. this q is a repeat, thank you tutors! i am really glad to stumble upon this site! really helps me a lot!]
Q:
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 reviewermath(1029) About Me  (Show Source):
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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:
Let X = number of customers between 4 and 7 P.M. on weekdays at the Safeway Supermarket in the South Strand area
a. No customers are waiting?
P(X = 0) = %28e%5E%28-4%29%29%284%5E0%29%2F0%21 = highlight%280.0183%29
b. Four customers are waiting?
P(X = 4) = %28e%5E%28-4%29%29%284%5E4%29%2F4%21 = highlight%280.1954%29
c. Four or fewer are waiting?
P(X ≤ 4) = sum%28%28e%5E%28-4%29%29%284%5Ex%29%2Fx%21%2C+x+=+0%2C+4%29 = highlight%280.6288%29
d. Four or more are waiting?
P(X ≥ 4) = 1 - P(X ≤ 3)
= 1+-+sum%28%28e%5E%28-4%29%29%284%5Ex%29%2Fx%21%2C+x+=+0%2C+3%29 = highlight%280.5665%29