Quality improvement efforts often make use of various mathematical mod
els that describe the relationships between quality characteristics an
d process factors. Such models typically come from a variety of source
s: experiments, theory, on-line data analysis, expertise, and other pr
ocess documents. These sources of knowledge are often distinct and sep
arate, often yielding models with slightly different predictions, havi
ng different precision and validity. In this paper we explore alternat
ives in which different mathematical models can be integrated together
into a single prediction that takes into account both model validity
and model variability. Some guidelines for establishing and quantifyin
g model validity are presented. The approach is demonstrated within th
e context of predicting surface finish in a machining process.