evaluating {HEAD ~ a difference} between the forecasted device performance characteristic and {TAIL ~ a target device performance characteristic}; and 
between
evaluating { HEAD ~ a difference } between the forecasted device performance characteristic and { TAIL ~ a target device performance characteristic } ; and
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH