associating a cause of said variation based upon a comparison of said one of said measured characteristics to measured characteristics associated with {HEAD ~ the remaining processing regions} of {TAIL ~ said subset} 
associating a cause of said variation based upon a comparison of said one of said measured characteristics to measured characteristics associated with { HEAD ~ the remaining processing regions } of { TAIL ~ said subset }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL