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Re: AI-GEOSTATS: Calculating averages

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  • Digby Millikan
    Calculating averagesCraig, Don t you mean multiply Average Nickel Head grade by Average Mill recovery. Your first figure 0.3342 is correct but your figure
    Message 1 of 3 , Jan 5, 2003
      Calculating averagesCraig,
      Don't you mean multiply Average Nickel Head grade by Average Mill
      recovery. Your first figure 0.3342 is correct but your figure 0.315963265
      is incorrect. It is your assumption that your average mill recovery is
      tonneage recovery, i.e. you averaged the mill recovery as if it where
      recovery per tonne of ore instead of per % of metal so your calculation
      of 0.5557*0.56857 is incorrect.

      Your average mill recovery should be calculated

      (0.53*60)+(0.65*62)+(0.32*20)+(0.8*70)+(0.56*63)+(0.45*55)+(0.58*0.68)/
      (0.53+0.65+0.32+0.8+0.56+0.45+0.58) =0.601465

      So your original table should look like;

      Nickel Mill Recovered
      Head Recovery Nickel
      Grade % (Ni %)
      0.53 60 0.3180
      0.65 62 0.4030
      0.32 20 0.0640
      0.8 70 0.5600
      0.56 63 0.3528
      0.45 55 0.2475
      0.58 68 0.3944
      Average 0.555714286 60.14652956 0.3342

      Average Nickel Head Grade
      divided by Average Mill Recovery ====> 0.334242857


      Regards Digby Millikan
      Geolite Mining Systems
      digbym@...
      http://www.users.on.net/digbym


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    • Isobel Clark
      Hi Craig The average of a product will only equal the product of the averages if the two numbers are completely independent of one another. This is exactly
      Message 2 of 3 , Jan 5, 2003
        Hi Craig

        The average of a product will only equal the product
        of the averages if the two numbers are completely
        independent of one another.

        This is exactly analogous to the calculation of a
        covariance in statistics.

        Isobel
        http://uk.geocities.com/drisobelclark

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