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12.4 Exercise 35

Avg difficulty 2.5

fXY(t,u)=12179(3t2+u)f_{X Y} \left(t , u\right) = \frac{12}{179} \left(3 t^{2} + u\right), for 0≤t≤20 \leq t \leq 2, 0≤u≤min{2,3-t}0 \leq u \leq \min \left\{2 , 3 - t\right\} (see Exercise 29 and Exercise 40 from "Problems on Mathematical Expectation").

Z = I M ( X , Y ) ( X + Y ) + I M c ( X , Y ) 2 Y 2 , M = { ( t , u ) : t ≤ 1 , u ≥ 1 } Z = I_{M} \left(X , Y\right) \left(X + Y\right) + I_{M^{c}} \left(X , Y\right) 2 Y^{2} , M = \left\{\left(t , u\right) : t \leq 1 , u \geq 1\right\}
E [ X ] = 2313 1790 , E [ Z ] = 1422 895 , E [ Z 2 ] = 28296 6265 E \left[X\right] = \frac{2313}{1790} , E \left[Z\right] = \frac{1422}{895} , E \left[Z^{2}\right] = \frac{28296}{6265}

Determine Var [Z]Var \left[Z\right] and Cov [X,Z]Cov \left[X , Z\right]. Check with discrete approximation.

Pfeiffer, Applied Probability, 12.4 Problems on Variance, Covariance, Linear Regression, exercise 35

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Adapted from Applied Probability © 2009 Paul E. Pfeiffer. Licensed under CC BY 3.0. Source: Applied Probability. Imported at revision d7a0420.