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