LetX1,X2 be two independent normal random variables with means μ1,μ2 and standard deviations σ1,σ2,respectively. ConsiderY=X1−X2,μ1=μ2=1,σ1=1,σ2=2.Then
A
Y is normally distributed with mean 0 and variance 1
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B
Y is normally distributed with mean 0 and variance 5
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C
Y has mean 0 and variance 5, but is NOT normally distributed
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D
Y has mean 0 and variance 1, but is NOT normally distributed
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Solution
The correct option is B Y is normally distributed with mean 0 and variance 5 ∵E(x1)=1=E(x2)andV(x1)=1
and V(x2)=4
Hence y is also normally distributed with mean 0 and variance 5