1

The question is regarding a given pair (X,Y) where x = 0,1,2... and y = x,x+1,x+2,... that have joint PMF of

Px,y(x,y) = (y ; x)*(e^-1)/((2^y)(y!))

I need to utilize this given equation to get marginal PMF of X and Y, and then for conditional PMF od y-x given X = x.

At first I realized that it has similarity toward poisson distribution so I try to relate to poisson. However the lambda values seems to be incorrect. because normally for poisson distribution the general formula is:

P=(e^-lambda)*(lambda^y)/(y!)

however from the above equation the two lamda are not the same. And another problem I'm not sure how to include the matrix column in the calculation.

Thanks for helping.

GarageN
  • 25
  • 3
    What is this (x;y)? – zoli Aug 07 '15 at 15:12
  • is a bracket like vector where x is on top and y is below. (x;y) is the way we write it in matlab – GarageN Aug 09 '15 at 04:32
  • There is a way we write in MSE: Am I interpreting well your formula:$$P_{X,Y}(x,y)=\begin{bmatrix}x\y\end{bmatrix}\frac{e^{-1}}{2^yy!}?$$ Learning how we write in MSE is useful because you get encquinted with $\LaTeX$ basics. Besides, $X,Y$ and $x,y$ are different objects. – zoli Aug 09 '15 at 07:59
  • Hi Zoli, yea that is how the x and y is, just that the bracket is a normal one ( ) instead of and square bracket [ ]. – GarageN Aug 10 '15 at 12:31
  • Does, then, $\left(\begin{matrix}x\y\end{matrix}\right)$ mean a vector? – zoli Aug 10 '15 at 12:34
  • the question does not state clearly, i'm not sure. But normally in such case will this be a vector or it is just part of the distribution like the (n k) bracket in front of binomial distribution? btw thanks a lot for keep helping – GarageN Aug 10 '15 at 12:38

0 Answers0