Exercise 13. Let X₁,..., Xn~ N(x, 02) i.i.d. and Y₁,..., Yn~ N(Hy, 02) i.i.d. with known o2. We assume that for each i the random variables X, and Y₁ are correlated, with Corr(X₁, Yi) = 1/2. Define D₁ = X₁ - Y; for all i E {1,...,n}. Finally, let X, Y and D be the averages of the X₁, Y₁ and Di, respectively. a) Show that Cov(X₁, Y₁) = 02/2. b) Determine E(D₁) and Var(D₁). c) Consider the test for Ho: z = Hy which uses the test statistic Z= √n- and which rejects Ho, if and only if |Z| > 1.96. Show that P(type I error) = 5%. d) In two or three sentences, discuss the differences between the test from part (c) on the one hand, and the non-paired test for comparing the means of two populations on the other hand.

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Exercise 13. Let X₁,..., Xn~ N(μ, 0²) i.i.d. and Y₁,..., Yn~ N(µy, o²) i.i.d. with known σ².
We assume that for each i the random variables X, and Y₁ are correlated, with Corr(X₁, Y₁) = 1/2.
Define D₂ = X₁ - Yį for all i € {1,...,n}. Finally, let X, Y and D be the averages of the X₁, Yi
and Di, respectively.
a) Show that Cov(X₁, Yi) = 0²/2.
b) Determine E(D₁) and Var(D₁).
c) Consider the test for Ho: a = μy which uses the test statistic
Z = √√n
and which rejects Ho, if and only if |Z| > 1.96. Show that P(type I error) = 5%.
d) In two or three sentences, discuss the differences between the test from part (c) on the one
hand, and the non-paired test for comparing the means of two populations on the other
hand.
2
Transcribed Image Text:Exercise 13. Let X₁,..., Xn~ N(μ, 0²) i.i.d. and Y₁,..., Yn~ N(µy, o²) i.i.d. with known σ². We assume that for each i the random variables X, and Y₁ are correlated, with Corr(X₁, Y₁) = 1/2. Define D₂ = X₁ - Yį for all i € {1,...,n}. Finally, let X, Y and D be the averages of the X₁, Yi and Di, respectively. a) Show that Cov(X₁, Yi) = 0²/2. b) Determine E(D₁) and Var(D₁). c) Consider the test for Ho: a = μy which uses the test statistic Z = √√n and which rejects Ho, if and only if |Z| > 1.96. Show that P(type I error) = 5%. d) In two or three sentences, discuss the differences between the test from part (c) on the one hand, and the non-paired test for comparing the means of two populations on the other hand. 2
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