Anonymous
Anonymous asked in 科學數學 · 2 decades ago

求算產品不合格比例

某產品的長度分配為平均數100 mm,標準差2 mm的常態分配,今銷售規格為 99 mm 加減5 mm,試求不合格的比例為何?

1 Answer

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  • ?
    Lv 7
    2 decades ago
    Favorite Answer

    Z = (X-mean)/standard deviation

    不及格為細於94及大於104

    細於94的機率

    Z = (94-100)/2

    Z = -3

    Area Z<-3 (by normal distribution table) 0.0013

    大於104的機率

    Z = (104-100)/2

    Z = 2

    Area Z>2 (by normal distribution table) 0.0228

    不及格機率為0.0013 + 0.0228 = 0.0241

    及格與不及格比 0.9759: 0.0241 = 約40.5 : 1

    Source(s):
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