At a checkout counter customers arrive at an average of 15 p

At a checkout counter customers arrive at an average of 1.5 per
minute. Find the probabilities that
a) at most 4 will arrive in any given minute;
b) at least 3 will arrive during an interval of 2 minutes;
c) at most 15 will arrive during an interval of 6 minutes.

Solution

  Y ~ Poisson (1.5)

a.       P(Y <= 4) = .7576

b.      P(Y >= 3/2)  = 1