X

-1 0 1

-1 0 0 (1/3)

Y 0 0 (1/3) 0

1 (1/3) 0 0

Now for this i am pretty sure my calculations are correct but i want to check because there seems to be some errors in the textxbook which confused me.

for the marginal PMF say of x, i simply thought i simply sum the coresponding column.

For example p{-1)=1/3

p(0)=1/3

p(1)=1/3

But when they do this in the book the value they obtain does not corespond to the sum of the column they are refering to, and this happens twice, and i dont think there would be two errors in the same question and hence i'm a bit confused now.

Next part to find E[XY] i multiply all values of x and y which gives me XY=-1,0,1, with corresponding probabilities.

Then to check if these random variables are independendant i check if E[XY]=E[x]E[Y]

which in this case is zero. so they must be independant. Can someone tell me if i am doing something wrong.