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Re: AI-GEOSTATS: large error correlation coefficient?

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  • Isobel Clark
    ... Sorry, that s not true. The error is independent of V1* but never of V1, especially if you are using a linear estimator such as kriging. ... This is known
    Message 1 of 2 , Jun 15 10:36 AM
      > I have performed a jacknife estimation of e variable
      > V1* in a 3D space, the reference file have the true
      > values of V1. Then I get the local error as
      > ERR=V1-V1*. The problem is that correlation
      > coefficient have large values for V1 and the other
      > variables (0.7-0.9) and by theory the error must to
      > be independent of the V1.
      Sorry, that's not true. The error is independent of
      V1* but never of V1, especially if you are using a
      linear estimator such as kriging.

      > Why it happen, it is really dangerous in resource
      > estimation?
      This is known as conditional bias and, in short, YES!

      This effect has been documented for 50 years and has
      variously been known as the regression effect, the
      mine call factor, the volume/variance effect,
      conditional bias and many other things (not all of
      them polite!).

      Isobel Clark
      http://geoecosse.bizland.com/whatsnew.htm

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