a = Assumed Maximum

b = Assumed Minimum

c = Raw Data St. Dev (Field Data)

d = Model Output (Research Data)

the formula used if the following

NORMSDIST (a-d) / (((c^2)+(b^2))^0.5)

Wondering why the data is being manipulated by the formula & what is accomplishing

Any help will be greatly appreciated. I can provide more detail if required

Cheers