Let (X1,Y1),(X2,Y2),…,(X20,Y20) be a random sample from the N2(0,0,1,1,frac34) distribution. Define bar X=frac120sumi=1^20Xi and bar Y=frac120sumi=1^20Yi. Then Var(bar X-bar Y) is equal to

Q24Section A (Section A)24 of 60

Variance of the difference of sample means

Let $(X_1,Y_1),(X_2,Y_2),…,(X_{20},Y_{20})$ be a random sample from the $N_2\bigl(0,0,1,1,\frac34\bigr)$ distribution. Define $\bar X=\frac1{20}\sum_{i=1}^{20}X_i$ and $\bar Y=\frac1{20}\sum_{i=1}^{20}Y_i$ . Then $\mathrm{Var}(\bar X-\bar Y)$ is equal to

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