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Ka wai 發問於 科學及數學數學 · 5 年前

Finite Math Question

If X is a normal random variable with mean 60 and standard deviation 20, find the

probability that X is between 89 and 106?

A..0581

B..0628

C..0665

D..8500

E..9158

1 個解答

評分
  • 5 年前
    最愛解答

    X ~ N(60, 20²)

    Pr( 89 < X < 106)

    = Pr{ (89 - 60)/20 < Z < (106 - 60)/20 }

    = Pr( 1.45 < Z < 2.3 )

    = Pr( 0 < Z < 2.3 ) - Pr( 0 < Z < 1.45 )

    = 0.4893 - 0.4265

    = 0.0628

    The answer is B.

    圖片參考:https://s.yimg.com/rk/HA00430218/o/201770806.gif

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