Suppose that X and Y are continuous random variables with joint pdf f (x, y) = e-**) 0

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**Introduction to Joint Probability Density Functions**

In this section, we will explore the concept of joint probability density functions (pdf) for continuous random variables through a given problem statement. 

### Problem Statement:

Suppose that \( X \) and \( Y \) are continuous random variables with joint pdf

\[ f(x, y) = e^{-(x+y)} \]
\[ 0 < x < \infty \text{ and } 0 < y < \infty \]
and zero otherwise.

Given this information, we aim to find the following probabilities:

a. Find \( \mathbb{P}(X > 3) \).  
b. Find \( \mathbb{P}(X > Y) \).  
c. Find \( \mathbb{P}(X + Y > 3) \).

### Explanation of the Joint PDF \[ f(x, y) \]:

The function \( f(x, y) = e^{-(x+y)} \) describes the joint probability density function of \( X \) and \( Y \). This indicates that the probability distribution is governed by the exponential of the negative sum of \( x \) and \( y \). The domain is restricted to positive \( x \) and \( y \), specifically \( 0 < x < \infty \) and \( 0 < y < \infty \). Outside this domain, the pdf is zero meaning no probability density is present outside the specified range.

**Visualizations:**

1. **Function Plot:** Imagine a 3D plot with \( X \) and \( Y \) on the horizontal axes and \( f(x, y) \) on the vertical axis. The plot will show that as either \( x \) or \( y \) increases, the value of \( f(x, y) \) decreases exponentially, indicating diminishing probability density further from the origin.

### Solution Approach:

To effectively solve the given queries, we will integrate the joint pdf within the specified boundaries, adhering to the constraints provided.

**a.** Finding \( \mathbb{P}(X > 3) \):

\[ \mathbb{P}(X > 3) = \int_{3}^{\infty} \left( \int_{0}^{\infty} e^{-(x+y)} \, dy \right) dx \]

**b.** Finding \( \mathbb{P}(X > Y) \):
Transcribed Image Text:**Introduction to Joint Probability Density Functions** In this section, we will explore the concept of joint probability density functions (pdf) for continuous random variables through a given problem statement. ### Problem Statement: Suppose that \( X \) and \( Y \) are continuous random variables with joint pdf \[ f(x, y) = e^{-(x+y)} \] \[ 0 < x < \infty \text{ and } 0 < y < \infty \] and zero otherwise. Given this information, we aim to find the following probabilities: a. Find \( \mathbb{P}(X > 3) \). b. Find \( \mathbb{P}(X > Y) \). c. Find \( \mathbb{P}(X + Y > 3) \). ### Explanation of the Joint PDF \[ f(x, y) \]: The function \( f(x, y) = e^{-(x+y)} \) describes the joint probability density function of \( X \) and \( Y \). This indicates that the probability distribution is governed by the exponential of the negative sum of \( x \) and \( y \). The domain is restricted to positive \( x \) and \( y \), specifically \( 0 < x < \infty \) and \( 0 < y < \infty \). Outside this domain, the pdf is zero meaning no probability density is present outside the specified range. **Visualizations:** 1. **Function Plot:** Imagine a 3D plot with \( X \) and \( Y \) on the horizontal axes and \( f(x, y) \) on the vertical axis. The plot will show that as either \( x \) or \( y \) increases, the value of \( f(x, y) \) decreases exponentially, indicating diminishing probability density further from the origin. ### Solution Approach: To effectively solve the given queries, we will integrate the joint pdf within the specified boundaries, adhering to the constraints provided. **a.** Finding \( \mathbb{P}(X > 3) \): \[ \mathbb{P}(X > 3) = \int_{3}^{\infty} \left( \int_{0}^{\infty} e^{-(x+y)} \, dy \right) dx \] **b.** Finding \( \mathbb{P}(X > Y) \):
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