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Probability

Variance

Concept Quizzes

Variance - Definition
Variance - Properties
Standard Deviation
Covariance
Covariance - Properties

Covariance

If the joint probability distribution function of $X$ and $Y$ is given as follows, what is $20 \text{Cov}(X,Y) ?$

$\begin{matrix} p(X,Y) & X=0 & X=1 & X=2 \\ Y=0 & 0.1 & 0.1 & 0.2 \\ Y=1 & 0.2 & 0.2 & 0 \\ Y=2 & 0 & 0.1 & 0.1 \end{matrix}$

4

1

2

0

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by Brilliant Staff

For random variables $X$ and $Y,$ which of the following is the same as $\text{Cov}(X,Y)?$

E[X]E[Y] - E[XY]

E[XY] -E[X] - E[Y]

E[XY] + E[X]E[Y]

E[XY] -E[X]E[Y]

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If the joint probability density function of continuous random variables $X$ and $Y$ is $f(x,y) = \frac{1}{6} \left( 8 x + 4 y \right)$ with $0 \le x \le 1 \text{ and } 0 \le y \le 1,$ what is the covariance between $X$ and $Y?$

\frac{1}{162}

- \frac{1}{162}

\frac{109}{162}

- \frac{109}{162}

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If $X$ and $Y$ are independent random variables where $E[X]=10$ and $E[Y]=8,$ what is $E[XY]?$

80 106 26 53

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If the probability distributions of continuous random variables $X$ and $Y$ are independent of each other, which of the following is equal to $\text{Cov}(X,Y)?$

E(XY)

E(X) + E(Y)

0

E(X)E(Y)

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