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Math Help - grouped frequency and quartiles

  1. #1
    Senior Member furor celtica's Avatar
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    May 2009
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    271

    grouped frequency and quartiles

    A company employs 2410 people whose annual salaries are summarised as follows:

    <10 10-20 20-30 30-40 40-50 50-60 60-80 80-100 >100 (i.e. 100-140)
    16 31 502 642 875 283 45 12 4

    First row: salary (in $1000)
    Second row: number of staff

    Find the upper and lower quartile.

    This should be fairly straightforward, I drew a quick cumulative frequency graph, came up with 603rd term for the lower quartile, 1808th term for the upper quartile; this is correct right?
    Anyway I got lower quartile around $30 130, upper quartile $47 700
    But the answers turned out to be $15 420 and $23 520 respectively, i.e. almost exactly half of each of the values I found.
    But how are those answers even possible, with the largest frequencies between 30 and 60? it just doesn't seem logical.
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  2. #2
    MHF Contributor Unknown008's Avatar
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    If those answers are given in the book, then I think that it's a misprint. Those cannot be the actual answers. Your answers seem correct to me.
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