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Normal Distribution

  1. Sep 15, 2010 #1
    I have a set of data that I used to create a histogram, and would like to fit it with a Gauss shape...I used the regular equation for a normal distribution, using the mean value and the standard deviation of my data, but the Gauss shape doesn't seem to be really fitting my data... I might be doing something wrong... I am attaching it here...

    Thanks!
     

    Attached Files:

  2. jcsd
  3. Sep 15, 2010 #2

    CRGreathouse

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    Science Advisor
    Homework Helper

    Yeah, the data doesn't look normal. Maybe it's a bimodal distribution of some sort?
     
  4. Sep 15, 2010 #3
    actually when I use the same of data on an online program I get better results...
    These are the numbers I am using:
    -2.1
    -1.8
    -1.6
    -1.4
    -1.2
    -1.1
    -1
    -0.9
    -0.8
    -0.7
    -0.5
    -0.4
    -0.3
    -0.2
    -0.1
    0
    0.1
    0.2
    0.3
    0.4
    0.5
    0.6
    0.7
    0.8
    0.9
    1
    1.8

    Do you know what the problem might be?
    PS: Try putting these numbers here: http://azzalini.stat.unipd.it/SN/sn-fit.html
    It gives a reasonable solution...

    Why isn't giving me similar solution? Any idea?
     
  5. Sep 16, 2010 #4

    statdad

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    Homework Helper

    I agree with CrGreatHouse - your data shouldn't be considered to be normally distributed.

    More importantly, if the data in your final post is your entire data set, the sample size is far too small to get a reliable idea of shape of the underlying distribution. A different type of graph (boxplot perhaps) would be a far better choice.
     
  6. Sep 16, 2010 #5
    What if I use a skew normal distribution... do you think that might fit the data better?
     
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