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4Q. The joint probability mass function of discrete random variables ๐‘‹ X and ๐‘Œ Y is given by: ๐‘ƒ [ ๐‘‹ = ๐‘ฅ , ๐‘Œ = ๐‘ฆ ] = { ๐‘˜ ( 4 ๐‘ฅ + ๐‘ฆ ) , ๐‘ฅ = 1 , 2 , 3 ย andย  ๐‘ฆ = 1 , 2 , 3 0 , otherwise P[X=x,Y=y]={ k(4x+y), 0, โ€‹ x=1,2,3ย andย y=1,2,3 otherwise โ€‹ Find the value of ๐‘˜ k. Then, calculate ๐‘ƒ ( ๐‘‹ = 2 ย andย  ๐‘Œ = 3 ) P(X=2ย andย Y=3).

Question

4Q. The joint probability mass function of discrete random variables ๐‘‹ X and ๐‘Œ Y is given by:

๐‘ƒ [ ๐‘‹

๐‘ฅ , ๐‘Œ

๐‘ฆ ]

{ ๐‘˜ ( 4 ๐‘ฅ + ๐‘ฆ ) , ๐‘ฅ

1 , 2 , 3 ย andย  ๐‘ฆ

1 , 2 , 3 0 , otherwise P[X=x,Y=y]={ k(4x+y), 0, โ€‹

x=1,2,3ย andย y=1,2,3 otherwise โ€‹

Find the value of ๐‘˜ k. Then, calculate ๐‘ƒ ( ๐‘‹

2 ย andย  ๐‘Œ

3 ) P(X=2ย andย Y=3).

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Solution

To find the value of k, we need to know that the sum of all probabilities in a probability mass function should be equal to 1.

Given that x and y can take values 1, 2, 3, we can write the total probability as:

Summation (x=1 to 3) Summation (y=1 to 3) P[X=x, Y=y] = 1

Substituting the given P[X=x, Y=y] = k(4x + y) into the equation, we get:

Summation (x=1 to 3) Summation (y=1 to 3) k(4x + y) = 1

Calculating the double summation, we get:

k[4(1+2+3) + (1+2+3)]*3 = 1 k[24 + 6]3 = 1 k90 = 1

So, k = 1/90.

Now, to calculate P(X=2 and Y=3), we substitute x=2 and y=3 into the equation P[X=x, Y=y] = k(4x + y):

P[X=2, Y=3] = k(4*2 + 3) = (1/90)*11 = 11/90.

This problem has been solved

Similar Questions

The joint distribution of ๐‘‹X and ๐‘ŒY is given byย  ย  ย  ย  ย  ย  ย  ย  ย  ย  ย  ย  ย  ย  ย ๐‘“๐‘‹๐‘Œ(๐‘ฅ,๐‘ฆ)=916ร—4๐‘ฅ+๐‘ฆ,f XYโ€‹ (x,y)= 16ร—4 x+y 9โ€‹ ,where ๐‘‡๐‘‹,๐‘‡๐‘Œโˆˆ{0,1,2,โ€ฆ}.T Xโ€‹ ,T Yโ€‹ โˆˆ{0,1,2,โ€ฆ}.1 pointFind the probability mass function of ๐‘‹+๐‘ŒX+Y.๐‘˜916โ‹…4๐‘˜k 16โ‹…4 k 9โ€‹ (๐‘˜+1)916โ‹…4๐‘˜(k+1) 16โ‹…4 k 9โ€‹ (๐‘˜+1)916โ‹…4๐‘˜+1(k+1) 16โ‹…4 k+1 9โ€‹ ๐‘˜916โ‹…4๐‘˜+1k 16โ‹…4 k+1 9โ€‹

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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 value of c. Find P(Y<X) and P(Y=X).

(30 points) Suppose Company 1's stock return ๐‘‹๐‘‹ is a random variable and takes three possiblevalues: {-0.1, 0.1, 0.2}. And Company 2's stock return ๐‘Œ๐‘Œ is a random variable and takes twopossible values: {-0.3, 0.4}. The joint probability distribution ๐‘“๐‘“(๐‘‹๐‘‹, ๐‘Œ๐‘Œ) is given as follows:๐‘“๐‘“(โˆ’0.1, โˆ’0.3) = 0.1, ๐‘“๐‘“(0.1, โˆ’0.3) = 0.2, ๐‘“๐‘“(0.2, โˆ’0.3) = 0.2,๐‘“๐‘“(โˆ’0.1,0.4) = 0.2, ๐‘“๐‘“(0.1,0.4) = 0.2, ๐‘“๐‘“(0.2,0.4) = 0.1.Please calculate the following:(a) Marginal distributions: ๐‘“๐‘“๐‘‹๐‘‹(๐‘ฅ๐‘ฅ) and ๐‘“๐‘“๐‘Œ๐‘Œ(๐‘ฆ๐‘ฆ). (4 points)(b) Mean: ๐ธ๐ธ(๐‘‹๐‘‹) and ๐ธ๐ธ(๐‘Œ๐‘Œ). (4 points)(c) Variance: ๐‘‰๐‘‰๐‘Ž๐‘Ž๐‘Ÿ๐‘Ÿ(๐‘‹๐‘‹) and ๐‘‰๐‘‰๐‘Ž๐‘Ž๐‘Ÿ๐‘Ÿ(๐‘Œ๐‘Œ). (4 points)(d) Covariance: ๐ถ๐ถ๐ถ๐ถ๐ถ๐ถ(๐‘‹๐‘‹, ๐‘Œ๐‘Œ). (2 points)(e) Conditional expectations: ๐ธ๐ธ(๐‘‹๐‘‹|๐‘Œ๐‘Œ = โˆ’0.3) and ๐ธ๐ธ(๐‘‹๐‘‹|๐‘Œ๐‘Œ = 0.4). (8 points)(f) Conditional variances: ๐‘‰๐‘‰๐‘Ž๐‘Ž๐‘Ÿ๐‘Ÿ(๐‘‹๐‘‹|๐‘Œ๐‘Œ = โˆ’0.3) and ๐‘‰๐‘‰๐‘Ž๐‘Ž๐‘Ÿ๐‘Ÿ(๐‘‹๐‘‹|๐‘Œ๐‘Œ = 0.4). (8 points)

Let X and Y be two random variables with joint probability mass function:P(X=i,Y=j) = (i+j)/36, for i,j=1,2,3,4What is the marginal probability mass function of X?Review LaterP(X=i) = 5(i+1)/36, for i=1,2,3,4P(X=i) = (5+i)/36, for i=1,2,3,4P(X=i) = 5/12, for i=1,2,3,4P(X=i) = (5i+1)/36, for i=1,2,3,4

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