1. A method of processing a run of workpieces, the method comprising the steps of: providing a database comprising subgroups of data representing characteristics from previously processed workpieces; selecting a first subgroup of data having characteristics that satisfy a predetermined criteria, wherein the selecting step includes: applying a set of rules to the database such that each rule generates a unique subgroup of data, wherein the rules are ordered according to a confidence level, and determining a subgroup of data of at least a minimum size that yields a highest confidence level among all of the rules; determining processing conditions for a processing tool corresponding to the first subgroup of data; processing the run of workpieces with the process tool using the determined processing conditions; and measuring the run of workpieces according to a sampling rate determined from the first subgroup of data.