Math Help - poisson

1. 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?

2. 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?
a) Poisson with mean 4/3. Calculate 1 - Pr(X = 0).

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