Question 971953
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) = {{{(e^(-4))(4^0)/0!}}} = {{{highlight(0.0183)}}}
b. Four customers are waiting?
P(X = 4) = {{{(e^(-4))(4^4)/4!}}} = {{{highlight(0.1954)}}}
c. Four or fewer are waiting?
P(X ≤ 4) = {{{sum((e^(-4))(4^x)/x!, x = 0, 4)}}} = {{{highlight(0.6288)}}}
d. Four or more are waiting?
P(X ≥ 4) = 1 - P(X ≤ 3)
         = {{{1 - sum((e^(-4))(4^x)/x!, x = 0, 3)}}} = {{{highlight(0.5665)}}}