Stuck again

Quote:

Originally Posted by nugiboy

http://i137.photobucket.com/albums/q...tiger/cars.jpg

Im now stuck on part (iii) of this question.

On part (i) i found:

$\overline{x}=0.5$

$Var[X]=0.545$

Im pretty sure these are right, and just check me on that if you can.

For part (ii), i just explained about there being a set time frame and a fixed average number of events per time frame, which i think is something to do with it.

I'm now really stuck on part (iii). I've got a couple of ideas which i think would give the right idea, but im still pretty unsure.

Any directions?

$f_n = 40 \Pr(X = n)$ where Pr(X = n) is calculated using the pmf for the Poisson distribution.