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Combining statistics from two distributions

  1. Mar 1, 2013 #1
    Is it possible to combine statistics from two distributions for the same parameter. For example I have one distribution for X from population A and a second distribution for X from population B. I want to assume all data is from the same population. I have calculated UTLs(Upper tolerance limits) for each population but need a single, combined utl for a combined population. The catch is I don't have the original data, only the calculated statistics.
     
  2. jcsd
  3. Mar 1, 2013 #2

    mfb

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    How is that upper tolerance limit defined?
    If you have some data about the distribution of the expected parameter (like mean+standard deviation and the assumption of a Gaussian distribution), you can combine both.
     
  4. Mar 1, 2013 #3
    According to the summary stats it is a normal distribution and the UTL is the 95% Upper tolrance Limit. i have the range of values and the artithmetic mean. No std dev.
     
  5. Mar 1, 2013 #4

    mfb

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    In that case, the standard deviation is just ~1/2 of the distance between mean and UTL. You can combine both values with a weighted average (the formula should be somewhere at wikipedia or on other pages. The weights are just the inverse variances.).
     
  6. Mar 1, 2013 #5
    Thank you. I will follow up on this.
     
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