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Mario

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# Find the constant k from the joint probability function of two random variables?

The joint PF of two discrete RVs X and Y is given by:

PXY(x,y) = k(2x+y) x=1,2; y=1,2

= 0 otherwise

How do I find the constant k?

I got k to be 1/18, but I don't know if that's right

thanks

### 1 Answer

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- kbLv 76 years agoFavorite Answer
Remember that the sum of all (nonzero) probabilities should equal 1.

So, we need

P(1, 1) + P(1, 2) + P(2, 1) + P(2, 2) = 1

==> 3k + 4k + 5k + 6k = 1

==> k = 1/18.

I hope this helps!

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