poisson

Vehicles arrive at a road junction at an average of 4 per min.
Assume that the vehicle arrivals are independent random events
and that the probability distribution does not change with time.
a) What is the probability that 1 or more vehicles arrive at the
junction in a 20 s interval?
(10)
b) What is the probability of having to wait less than 2 min for a
vehicle to arrive at the junction?

Quote:

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Originally Posted by Haris

Vehicles arrive at a road junction at an average of 4 per min.
Assume that the vehicle arrivals are independent random events
and that the probability distribution does not change with time.
a) What is the probability that 1 or more vehicles arrive at the
junction in a 20 s interval?
(10)
b) What is the probability of having to wait less than 2 min for a
vehicle to arrive at the junction?

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a) Poisson with mean 4/3. Calculate 1 - Pr(X = 0).

b) Read this. Now calculate Pr(Y < 2).