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Given Y = 3 − 2X, E[X] = 5, and Var(X) = 4, which statement is correct?

Mathematics

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Step-by-step solution

3 steps
  1. Calculate the expected value of YY, E[Y]E[Y].

    Given the linear transformation Y=aX+bY = aX + b, the expected value is E[Y]=aE[X]+bE[Y] = aE[X] + b.
    In this case, Y=3−2XY = 3 - 2X, so a=−2a = -2 and b=3b = 3.
    We are given E[X]=5E[X] = 5.

    E[Y]=E[3−2X]=3−2E[X]E[Y] = E[3 - 2X] = 3 - 2E[X] E[Y]=3−2(5)E[Y] = 3 - 2(5) E[Y]=3−10E[Y] = 3 - 10 E[Y]=−7E[Y] = -7
  2. Calculate the variance of YY, Var(Y)Var(Y).

    Given the linear transformation Y=aX+bY = aX + b, the variance is Var(Y)=a2Var(X)Var(Y) = a^2 Var(X).
    In this case, Y=3−2XY = 3 - 2X, so a=−2a = -2.
    We are given Var(X)=4Var(X) = 4.

    Var(Y)=Var(3−2X)=(−2)2Var(X)Var(Y) = Var(3 - 2X) = (-2)^2 Var(X) Var(Y)=(4)(4)Var(Y) = (4)(4) Var(Y)=16Var(Y) = 16
  3. Compare the calculated values with the given options.

    Our calculations show E[Y]=−7E[Y] = -7 and Var(Y)=16Var(Y) = 16.
    Option D states: E[Y]=3−2E[X]=−7E[Y] = 3 - 2E[X] = -7 and Var(Y)=(−2)2Var(X)=16Var(Y) = (-2)^2 Var(X) = 16. This matches our results.

    The correct statement is D.

    D. E[Y]=3−2E[X]=−7 and Var(Y)=(−2)2Var(X)=16\boxed{\text{D. } E[Y] = 3 - 2E[X] = -7 \text{ and } Var(Y) = (-2)^2 Var(X) = 16}
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