Cars arrive to a gas station according to a Poisson distribution with a mean of 4 cars per hour. Use Excel or StatCrunch to solve.
a. What is the expected number of cars arriving in 2 hours, or λt?
b. What is the probability of 6 or less cars arriving in 2 hours? ROUND TO FOUR (4) DECIMAL PLACES.
c. What is the probability of 9 or more cars arriving in 2 hours? ROUND TO FOUR (4) DECIMAL PLACES.
(A) Expected number of cars arriving in 2 hours = (number of cars per hour)*(number of hours)
= 4*2
= 8 cars per 2 hours
(B) Probability of 6 or less can be found directly using POISSON function in excel
Using excel function POISSON(x,mean,cumulative)
setting x = 6, mean = 8 and cumulative =TRUE for 6 or less
this implies
= POISSON(6,8,TRUE)
= 0.3134
(C) Probability of 9 or more = 1 - Probability of at least 8
= 1 - POISSON(x,mean,cumulative)
setting x = 8, mean = 8 and cumulative =TRUE for 6 or less
this implies
= 1 - POISSON(8,8,TRUE)
= 1-0.5925
= 0.4075
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