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Math Help - Chi Square test and Failure Rate Questions

  1. #1
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    Chi Square test and Failure Rate Questions

    [/SIZE][/FONT] Given a target mean of 100, a standard deviation of 1 when the process is in control, and the product is acceptable between the range of 97 to 103. A measurement outside this range is a failure.



    If the process is in control, how many failures do you expect out of every 10,000 items produced?
    Last edited by ChrisYee08; May 17th 2011 at 02:16 PM.
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  2. #2
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    Is that 97 to 103 a 95% confidence interval for the mean?
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  3. #3
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    it doesnt say, thats all the information it gives you.
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  4. #4
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    O.K. Its been a while since I did a quality control course (assuming that is what you are doing?) but you could work backwards to find an initial n using the rule for a confidence interval and then determine if this sample size is big enough to map back to n= 10,000.
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  5. #5
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    to calculate the z value i used 103 = 100+z(SD/SQRT(n)) => 3 = z(1/100) => z = 300 which doesnt make much sense to me.
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  6. #6
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    I think there's more to the question than what I can offer at this point (unless I starting digging through my undergrad notes) but if this is a 95% confidence interval then

    \displaystyle 103 = 100 + 1.96 \times \frac{1}{\sqrt{n}} then solve for n
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  7. #7
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    yea that doesnt work sorry. the answer is 26 tho if that helps.
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