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Combining Random Variables

AP Statistics· difficulty 3/5

X and Y are independent with means 5 and 8, variances 4 and 9.

X mean = 5 var = 4 Y mean = 8 var = 9 X, Y independent

What is the SD of X + Y?

  • A

    5

  • B

    sqrt(5)

  • C

    13

  • D

    sqrt(13)

    check_circle

Explanation

Var(X+Y) = Var(X) + Var(Y) = 4 + 9 = 13. SD = sqrt(13).

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