Alluvial gold grades are typically highly erratic. It is very often difficult to establish with confidence the in situ grades of reserve blocks due to the small number of pit or drill hole samples available, and their erratic values._x000D_
Trends in grade are often obscure._x000D_
Geostatical methods are inappropriate due to the extreme nugget effect found in alluvial gold field data. Classical statistics appear more suited to such data but require assumptions to be made regarding the nature of the population sampled._x000D_
Recent developments in computer intensive non-parametric statistical methods provide a new approach to dealing with some of the above problems. These methods avoid making assumptions about the type of population distribution, usually through some kind of re-sampling scheme._x000D_
The bootstrap procedure involves taking the estimate of interest and synthesising its population of by re-sampling the original data a large number of times (1000+), at random and with replacement. The synthetic population is then used to draw conclusions about the likely behaviour of the true population.