How Do You Calculate P(X>4Y) with the Given Joint PDF?

In summary, the joint probability density function for X and Y is given by f(x,y) = x+4y, 0<y<x<1 and the task is to find the probability P(X>4Y). The marginal probability density functions for X and Y are p1(x) = 3x^2 and p2(y) = (-9/2)y^2+4y+(1/2), respectively. However, they may not be relevant for this question. Instead, an equation should be written using the given f(x,y) to solve for P(X>4Y).
  • #1
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Homework Statement



Suppose X and Y have the joint probability density function:

f(x,y) = x+4y, 0<y<x<1
f(x,y) = 0 otherwise

Find P(X>4Y)

Homework Equations





The Attempt at a Solution



I'm not sure how to do this. I've already found marginal pdf's for x and y.. although I don't know if they're relevant.

p1(x) = 3x^2
p2(y) = (-9/2)y^2+4y+(1/2)

Thanks for the help
 
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  • #2
I agree with your values for the marginals. Although I don't think they are relevant for this question.. There may be a way to do it, making use of the marginals, but that is not the way I did it.

You should start by writing an equation for P(X>4Y) using the equation f(x,y)
 

Related to How Do You Calculate P(X>4Y) with the Given Joint PDF?

1. What is the formula for finding P(X>4Y) given joint pdf?

The formula for finding P(X>4Y) given joint pdf is P(X>4Y) = ∫∫ p(x,y) dx dy, where p(x,y) is the joint probability density function.

2. How is the joint pdf related to the probability of X and Y?

The joint pdf represents the probability of both X and Y occurring simultaneously. It is a function that assigns a probability value to every point in the X-Y plane.

3. Can the joint pdf be used to find other probabilities?

Yes, the joint pdf can be used to find other probabilities by integrating over the desired region in the X-Y plane. For example, to find P(X>4Y), we would integrate over the region where X>4Y.

4. What is the difference between P(X>4Y) and P(X,Y>4)?

The difference between P(X>4Y) and P(X,Y>4) is that the former represents the probability of X being greater than 4 times Y, while the latter represents the probability of both X and Y being greater than 4.

5. Can P(X>4Y) be greater than 1?

No, P(X>4Y) cannot be greater than 1 as it represents a probability and probabilities cannot exceed 1. It is possible for the integral to be greater than 1, but this would indicate an error in the calculation.

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