CHAPTER 4: Estimation
SUMMARY
OF MAJOR POINTS
1.
When an estimation is performed, an error is made in
the prediction.
2. The magnitude of that error is
dictated by the structure and type of the deposit, and by the mineral itself.
Different minerals within the same deposit may have different structures.
3. The structure can (probably) be
described by a semi-variogram model, in the absence of significant trend on the
local level.
4. The estimation error variance can
be calculated if the semi-variogram model is known. Tables for the spherical
model have been supplied. These may also be used as approximations for the
linear model.
5. If we use the extension type of
estimator, i.e. the arithmetic mean of the samples, then the extension variance
may be written:
That is, the ‘reliability’ of the
estimator depends on three quantities: the relationship of the samples to the area
to be estimated; the relationship amongst the samples; and the variation of
grades within the area being estimated.