The present invention provides a method and apparatus for integrating multiple sample plans. The method includes receiving a first wafer state data set from an in situ wafer measurement device, the first wafer state data set being indicative of at least one characteristic of at least one wafer processed by a processing tool and receiving a second wafer state data set from an ex situ wafer measurement device, the second wafer state data set being indicative of the at least one characteristic of the at least one wafer processed by the processing tool. The method also includes forming a third wafer state data set using the first and second wafer state data sets and determining the at least one characteristic of the at least one wafer based upon the third wafer state data set.