Selected Topics for Further Research - Geomathematics: Theoretical Foundations, Applications and Future Developments - page 482

Fig. 12.10 Cumulative frequency distributions (lognormal Q-Q plots) of gold and arsenic in
379 till samples, Southern Saskatchewan. Units of Au and As concentration values are ppb and
ppm, respectively (Source: Agterberg 2007a , Fig. 7)
Fig. 12.11 Straight line fitted to part of lognormal Q-Q plot of gold values shown in Fig. 12.12 .
Inverse of slope provides estimate of logarithmic (base e ) standard deviation (Source: Agterberg
2007a , Fig. 8)
consists of fitting a straight line on the Q-Q plot. Figure 12.11 shows such a line of
best fit for Au. Because natural logarithms are used, the standard deviation of
logarithmically transformed concentration values can be set equal to the inverse
of the slope of the best-fitting straight line. It amounts to 2.37 ppb for Au. Difference
in shape of frequency distribution is reflected in the fact that the logarithmic
variance of Au is more than 40 times as large as the logarithmic variance of As