Math Problem Statement
The joint probability distribution table for two random variables X and Y is as follows Y X -2 -1 4 5 1 0.1 0.2 0 0.3 0.1 0.1 0 2 0.2 Determine the marginal probability distributions of X and Y. Also compute (a) Expectations of X and Y (b) Standard deviation of X and Y (c) Covariance of X and Y (d) Correlation of X and Y.
Solution
We are given a joint probability distribution table for two random variables and . Let's extract the values first to determine the marginal distributions, expectations, standard deviations, covariance, and correlation.
1. Joint Probability Distribution Table
Y / X | -2 | -1 | 4 | 5 | Marginal |
---|---|---|---|---|---|
1 | 0.1 | 0.2 | 0 | 0.3 | |
0 | 0.1 | 0.1 | 0 | 0 | |
2 | 0 | 0 | 0.2 | 0 |
Step 1: Marginal Probability Distributions of X and Y
- Marginal probability distribution of
We sum over all the values of for each value of :
Thus, the marginal distribution of is:
1 | 0 | 2 | |
---|---|---|---|
0.6 | 0.2 | 0.2 |
- Marginal probability distribution of
We sum over all the values of for each value of :
Thus, the marginal distribution of is:
-2 | -1 | 4 | 5 | |
---|---|---|---|---|
0.2 | 0.3 | 0.2 | 0.3 |
Step 2: Expectations of and
- Expectation of
- Expectation of
Step 3: Standard Deviation of and
- Variance of
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Math Problem Analysis
Mathematical Concepts
Probability Theory
Marginal Distributions
Expectation
Variance
Covariance
Correlation
Formulas
Marginal distribution of X: P(X = x) = Σ P(X = x, Y = y)
Expectation of X: E(X) = Σ x * P(X = x)
Variance of X: Var(X) = E(X^2) - [E(X)]^2
Covariance: Cov(X, Y) = E(XY) - E(X)E(Y)
Correlation: Corr(X, Y) = Cov(X, Y) / (σ_X * σ_Y)
Theorems
Law of Total Probability
Covariance and Correlation Definitions
Suitable Grade Level
Undergraduate Level (Probability and Statistics)
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