Most mineral processes have autocorrelation (tonnage now depends on tonnage 5 minutes ago). Traditional X-bar-R charts are less useful; charts are superior because they detect small, persistent shifts.
“You taught us the math and the models,” Lin said. “But more than that — you taught us to treat uncertainty like information, not an obstacle.” Statistical Methods For Mineral Engineers
Traditional statistics treats data points as independent. Geostatistics, founded by Georges Matheron based on Danie Krige’s work in the South African gold mines, acknowledges that samples close together are more similar than samples far apart . Statistical Methods For Mineral Engineers