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31Re: AI-GEOSTATS: In need of some help.

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  • Yong Wang
    Dec 20, 2000
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      Mann-Whitney U test does require that the distributions of two populations
      are similar. It is distribution free but not assumption free.

      Resampling (or randomization) methods should work. Basically, you will mix
      the two samples, and then randomly separate them into two groups, and
      calculate the parameter you are interested (e.g., average difference);
      repeated the process for a large number of times. You will get a
      distribution of the parameter, compare the parameter estimate from original
      data with this distribution to see how likely you would be able to get the
      original value by chance.

      You can run this through Excel by set up a macro. Or check
      www.resample.com, there is information about the methods and software.

      Best,

      Yong Wang





      At 10:08 AM 12/19/00 -0700, mercury1@... wrote:
      >
      >Hi Folks!
      >This is my first post to this list. Hope it is not out of place. I need a
      >way to compare two small populations (very small sample sizes..5 and
      6....both
      >of which lack normality). I would like to compare them based on 3-5
      parameters.
      > Because of the above limitations I have given up on the validity of a t-test
      >(which assumes a normal distribution and larger sample sizes). My basic
      question
      >is this: are these two small populations statistically different or do they
      >belong to the same population? I have asked many elementary level stats
      folks
      >and have not been entirely satisfied with their solutions. So, I pose this
      >'problem' to you.
      >Thanks for your time.
      >Happy Holidays!
      > -Harland
      >
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