Context: The random variables X and Y have the joint PMF: px,y(x, y)=c*(x+y)^(2) if x belongs to {1,2,4} and y belongs to {1,3} and otherwise px,y(x,y) =0. Find the expectations E[XY].
Question
Context: The random variables X and Y have the joint PMF: px,y(x, y)=c*(x+y)^(2) if x belongs to {1,2,4} and y belongs to {1,3} and otherwise px,y(x,y) =0. Find the expectations E[XY].
Solution
To find the expectation E[XY], we need to sum over all possible values of x and y, the product of x, y and their joint probability.
The expectation E[XY] is given by the formula:
E[XY] = Σ (x * y * p(x, y))
where the sum is over all possible values of x and y.
Given the joint PMF p(x, y) = c*(x+y)² for x ∈ {1,2,4} and y ∈ {1,3}, we can substitute this into the formula:
E[XY] = Σ (x * y * c*(x+y)²)
We can calculate this sum explicitly by summing over the given values of x and y:
E[XY] = c * [11(1+1)² + 13(1+3)² + 21(2+1)² + 23(2+3)² + 41(4+1)² + 43(4+3)²]
Simplify this expression to get the value of E[XY].
Note: The value of c is not given in the problem. If it was given, we could substitute it into the expression to get a numerical value for E[XY]. If it's not given, E[XY] will be an expression in terms of c.
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