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Re: [ai-geostats] Re: Sill versus least-squares classical variance estimate

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  • Meng-Ying Li
    Hi Digby and All, I did a little experiment on the idea that Digby mentioned: The sill will estimate the population variance, but found it not true in my
    Message 1 of 18 , Dec 8, 2004
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      Hi Digby and All,

      I did a little experiment on the idea that Digby mentioned: The sill will
      estimate the population variance, but found it not true in my experiment:

      1. I generated a set of one-dimentional data with 27 points on regular
      unit spacings, which I'd like to take it as the true, or population
      value. On purpose, I generate the data so it has an influence range of
      three length units.
      2. I calculated the experimental variogram. Notice that the variogram is
      the population variogram. The sill value is around 2.8.
      3. But the population variance is 2.39, lower than the sill value.

      This confirms my doubt about using sill value as the estimate of
      population variance, since I calculate the variogram and variance based on
      all data points. Please tell me what you think. The data I generated are
      as follows:

      0.056970748
      0.14520424
      0.849710204
      1.650514605
      1.101666385
      1.015177986
      2.150259206
      2.830780659
      0.223495817
      -2.47615958
      -3.372697392
      -0.530685611
      0.786582177
      0.970673
      0.674755256
      0.338461632
      1.020874834
      0.410936991
      1.702892405
      2.649748012
      4.290179731
      3.442015668
      1.488818953
      0.862788738
      0.728709892
      2.398182914
      1.522546427
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