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Combining Random Variables

AP Statistics· difficulty 2/5

X has mean 20, variance 9. Let W = 2X.

Quantity Value mean(X) 20 Var(X) 9 W = 2X Var(W)?

What is the variance of W?

  • A

    18

  • B

    81

  • C

    36

    check_circle
  • D

    9

Explanation

Var(aX) = a^2 Var(X) = 4 * 9 = 36.

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