Small sample support sizes certainly tend to have higher nugget effects and if the kriging of an ore block is then done with an inadequate data search routine, the problem of ‘conditional biases’ will be exaggerated. Block estimates done on this basis should not be labeled ‘kriging’ or even ‘geostatistics’. Conditional biases occur whatever the individual sample support size and arises basically from an inadequate data search routine when estimating the grades of ore units (blocks). Dr. Manns’ connection between ‘conditional bias’ and a ‘random value’ is not understood.

I have never encountered any problems with the log-normal model or...

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