
Poisson Distribution
Suppose that the number of inquiries arriving at a certain interactive system follows a Poisson distribution with arrival rate of 12 inquiries per minute. Find the probability of 10 inquiries arriving
(a) in a 1minute interval
(b) in a 3minute interval
I am unsure if the rate is 60/12 or 12/60.

just keep it in minutes
$\displaystyle \lambda=12$ in part a and $\displaystyle \lambda=36$ in part b
$\displaystyle P(X=x)={e^{\lambda}\lambda^x\over x!}$
(a) $\displaystyle P(X=10)={e^{12}{12}^{10}\over (10)!}$
(b) $\displaystyle P(X=10)={e^{36}{36}^{10}\over (10)!}$