VIc
Lv 7
VIc 發問於 科學及數學數學 · 8 年 前

math-normal distribution

A set of concrete cubes with the random strengh variable X~N(39,42),find the probability of strength X between 30mPa and 42mPa.

1 個解答

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  • 8 年 前
    最佳解答

    Answer: 0.595824

    Pr (30 <= X <= 42)

    = Pr( (30 - 39)/√42 < Z < (42 - 39)/√42 )

    = Pr( -1.3887 < Z < 0.46291 )

    = 0.595824

    So, the probability of strength X between 30mPa and 42mPa is 0.595824

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