Marginal Density Fx (x)

In summary, we need to calculate the marginal density of fx (x) using the given distribution of Fx,y (x,y). The equation is set up as fx (x) = integral from x up to infinity of 4x.e^(x+y) dy, but there seems to be an issue with infinity in the problem. The correct answer is 4x.e^(-2x) and there may be a missing minus sign in the original distribution.
  • #1
qwertydh
1
0

Homework Statement



Calculate the marginal density of fx (x).
Fx,y (x,y) = double integral of 4x.e^(x+y) when 0<x<y, 0 otherwise.


Homework Equations





The Attempt at a Solution



i set up the equation as fx (x) = integral from x up to infinity of 4x.e^(x+y) dy

i get 4x [e^(x+y)] from x to infinity,

thats when the problem arises as whatever i do there's always infinity in the question.

I'm told the answer is 4x.e^(-2x)

any help would be really appreciated.
thanks.
 
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  • #2
are you sure you haven't missed a minus sign in the original distribution>
[tex] f_{X,Y} (x,y)dxdy = 4xe^{-(x+y)}dx dy [/tex]

would make more sense, the distrubution you gave is unbounded
 

1. What is Marginal Density Fx (x)?

Marginal Density Fx (x) is a mathematical concept used in probability and statistics to describe the probability distribution of a single variable in a multi-dimensional system. It represents the probability of a specific value of that variable occurring.

2. How is Marginal Density Fx (x) calculated?

Marginal Density Fx (x) is calculated by integrating the joint probability distribution function over all possible values of the other variables in the system, leaving only the variable of interest. This results in a one-dimensional probability distribution for that variable.

3. What is the difference between Marginal Density Fx (x) and Conditional Density Fx (x|y)?

Marginal Density Fx (x) represents the probability distribution of a single variable in a multi-dimensional system, while Conditional Density Fx (x|y) represents the probability distribution of a variable given another variable's specific value. Marginal Density Fx (x) integrates over all other variables, while Conditional Density Fx (x|y) holds the other variable constant.

4. How is Marginal Density Fx (x) used in statistical analysis?

Marginal Density Fx (x) is used to determine the probability of a specific value occurring for a variable in a multi-dimensional system. It is also used to calculate summary statistics, such as mean and variance, for that variable.

5. What are some real-world applications of Marginal Density Fx (x)?

Marginal Density Fx (x) has many applications in fields such as finance, economics, and engineering. It is used to model and analyze various systems, such as stock prices, economic indicators, and physical processes, to make predictions and inform decision-making.

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