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Homework Help: Mean, median, Mode, standard deviation and 10th and 90th percentiles!

  1. Jun 23, 2010 #1
    1. The problem statement, all variables and given/known data

    I have two sets of data, each with 30 distances and 30 results, I have the mean, median, mode, range etc, I have drawn histograms and cumulative frequency curves, got the IRQ for both sets of data.

    Now I need to compare the data using standard deviations and also find the 10th and 90th percentiles, could you explain the EASIEST way to do this without having to write a lot more things down, is there a formula or equation to get both these things.

    Also how would I superimpose smooth curves to represent data distributions on the histograms and mark on the means, what data would I use and how would I identify skewness if any.

    I just want descriptions on the easiest way to achieve this, I have not provided any numbers/data as i don't want you to do my work for me, rather just to give me the method in which I can do it myself.

    Any help is greatly appreciated.

  2. jcsd
  3. Jun 24, 2010 #2
    To find the 10th and 90th percentile, use the definition. The score at the 90th percentile means it is higher than 90% of the data; in your case higher than 27 of the data points.
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