{HEAD ~ Target web site data values} are compared to {TAIL ~ average and bounding web site data values} at a given time 
are compared to
{ HEAD ~ Target web site data values } are compared to { TAIL ~ average and bounding web site data values } at a given time
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH