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Cumulative frequency graph

  1. Jan 22, 2014 #1

    adjacent

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    1. The problem statement, all variables and given/known data
    Height- 1-10| 10-20 |30-50 |50-60
    Frequency 2 |5| 7| 9
    Cumulative frequency-2 7 14 18
    So this is a Group frequency table.
    Is the median obtained from Cumulative frequency graph 100% accurate?Or is it just an assumption?


    2. Relevant equations



    3. The attempt at a solution
    We don't know the exact height value.So we put the largest value in the class.
    So if just consider the first column,
    The height of the first person(Frequency 1) should be 5.But we don't know that.He may or may not be 5feet(or whatever) tall
     
  2. jcsd
  3. Jan 22, 2014 #2

    Ray Vickson

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    According to your table there is nobody between 20-30 units (whatever those are). Is that really the case?

    Anyway, if you categorize more finely, you will get a different median. For example, if you use class boundaries 1-2, 2-3, 3-4, ...., 59-60 the answer will almost surely be different. In the first case you median will be accurate to +-5, and in the second case accurate to +-0.5 .
     
  4. Jan 22, 2014 #3

    adjacent

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    I just made up a graph from no where.It's the reason

    So it is an approximation.
     
    Last edited by a moderator: Jan 22, 2014
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