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Finding a percentile ranking

  1. Sep 27, 2009 #1
    1. The problem statement, all variables and given/known data

    60% of all machines inspected were 20 years or older. Give a percentile ranking for the age of 20 years in the distribution of all ages of inspected machines.

    2. Relevant equations

    Don't think there are any that apply to this question :/

    I found this equation:

    Precentile rank = (B + 0.5E) / n

    ...where B = number of scores below x, E = number of scores equal to x, n = number of scores, and x is the percentile rank you want to find (http://www.regentsprep.org/regents/math/algebra/AD6/quartiles.htm)

    But I can't really plug anything in.

    3. The attempt at a solution

    Maybe this is more on the intuitive side, or I'm not understanding the question. It seems like more variables have to be given, as there isn't much to do!

    60% were 20 years or older, so 40% were less than 20. Now what? I'd need to know the total number of scores, wouldn't I?
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
  3. Oct 2, 2009 #2
  4. Nov 29, 2009 #3
    One last bump.

    I really need some guiding words!
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