Introduction

ØThe quantity being determined is defined by Y
lParameters (inputs) used to describe Y are X1, X2, X3 É Xi. 
lThese quantities are estimated by the terms y, x1, x2, x3 Éxi.
ØUncertainties
lThe standard uncertainty of an input is u(xi)
lThe combined standard uncertainty is uc(y),
lThe expanded uncertainty is the value which is reported.