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Median interpolation on logarithmic data

  1. Sep 14, 2009 #1
    1. The problem statement, all variables and given/known data
    Hello, I have a set of data that is grouped into bins. The bin sizes increase logarithmically by 10% (1.1 x the previous bin).


    2. Relevant equations
    Bin
    Mean
    Radius Frequency
    1.03 4924
    1.10 9938
    1.21 14009
    1.32 12269
    1.44 15813
    1.58 18723
    1.74 21471
    ... ...

    My total frequency is 612574
    I used excel's frequency function. For the first group any data that is greater than 1.03 and less than 1.10 is put into that group. So you can write it

    1.03<= x < 1.10

    so the lower class boundary is 1.03

    3. The attempt at a solution

    using the median interpolation formulae

    lower class boundary + ((n/2*[culmalative frequency of the previous classes])/frequency of class) * class width

    So for the 10% percentile:

    it lies in class 1.58.

    1.58 + (((612574/2)-56953)/18723) . (1.74 - 1.58)

    = 3.7107

    Which cannot be. Is this because im using logarithmic data? Is there a more suitable way?
    Thanks
     
  2. jcsd
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