Look at the volume:
"Volume: As the pattern unfolds, plays an important role in confirmation. can be measured as an indicator (OBV, ) or simply by analyzing levels. Ideally, but not always, during the advance of the left shoulder should be higher than during the advance of the head. This decrease in and the new high of the head, together, serve as a warning sign. The next warning sign comes when increases on the decline from the peak of the head. Final confirmation comes when further increases during the decline of the right shoulder."