Hi Sushi2008,

It seems reasonable to assume the number of hits per time period has a Poisson distribution, so X has a Poisson distribution with mean 3. This is also the variance.

To find P(X >= 2), use P(X >= 2) = 1 - P(X=0) - P(X=1) and the formula for the pdf of a Poisson distribution.

If Y also has a Poisson distribution with mean 3, then X+Y has a Poisson distribution with mean 6 (and variance 6).

To find E[(X+Y)^2], use var(X+Y) = E[(X+Y)^2] + [E(X+Y)]^2.

Hope this helps,

jw