Determine the values of c so that the following functions represent joint probability distributions of the random variables X and Y : (a) f(x,y)=cxy, forx =1 ,2,3; y =1 ,2,3; (b) f(x,y)=c|x−y|, forx = −2,0,2; y = −2,3.

Respuesta :

Answer:

The joint probility density will be c = 1/36

The joint probability distribution will be c = 1/15

Step-by-step explanation:

For step by step explanation see the pucture attached

Ver imagen madihasaadmamoon
Ver imagen madihasaadmamoon

Following are the solution to the given question:

To be valid probability functions, the sum of changes across the entire range of x and y variables must equal one.

For point a)

In this case, the cumulative probability density might be represented as follows:

                   [tex]x=1 \ \ \ \ \ \ \ \ \ \ \ \ \ x=2 \ \ \ \ \ \ \ \ \ \ \ \ \ x=3\\\\[/tex]

[tex]y=1 \ \ \ \ \ \ \ \ \ \ \ \ \ c \ \ \ \ \ \ \ \ \ \ \ \ \ 2c \ \ \ \ \ \ \ \ \ \ \ \ \ 3c\\\\y=2 \ \ \ \ \ \ \ \ \ \ \ \ \ 2c \ \ \ \ \ \ \ \ \ \ \ \ \ 4c \ \ \ \ \ \ \ \ \ \ \ \ \ 6c\\\\y=3 \ \ \ \ \ \ \ \ \ \ \ \ \ 3c \ \ \ \ \ \ \ \ \ \ \ \ \ 6c \ \ \ \ \ \ \ \ \ \ \ \ \ 9c\\\\[/tex]

As just a result, the overall number of probability equals

 [tex]= c (1 + 2 + 3 + 2 + 4 + 6 + 3 + 6 + 9) = 36c[/tex]

The sum must now equal one of these for it to be legal. As a result,

[tex]36c = 1 \\\\c = \frac{1}{36}[/tex]

For point b)

In this case, the joint probability could be represented as follows:

                       [tex]x= -2 \ \ \ \ \ \ \ \ \ \ \ x=0 \ \ \ \ \ \ \ \ \ \ \ x=2 \\\\[/tex]

[tex]y=-2 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 0 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 2c\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 4c \\\\y=3 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 5c\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 3c \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ c[/tex]

As a consequence, the total likelihood in this case is:

[tex]\to c ( 2 + 4 + 5 + 3 + 1) = 15 c\\\\\to 15c = 1 \\\\c = \frac{1}{15}[/tex]

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