guys, i have a question about assays and average gold/ton..

in the past i have heard that if assays from a core sample come back at say 100g/ton they are excluded from the average as an "anomoly"...how does this work?

i mean, from what i gather the cores containing visible gold may very likely come back showing very high grade, as well they should....

but how do they decide what is an anomoly and what's not?

i.e. if 5 samples contain 100g/ton and 45 samples contain 0g/ton would'nt that give you an average of 10g/ton?

any thoughts?