The determination is also based upon the assumption that the opposition will double the sacrifice bid thereby increasing the penalty points.
For example, after the partner opens 1♦ and RHO doubles, the following hand is suitable for a bid of 5♦, outbidding opponents' major suit game in advance: As seen in the table above, vulnerability significantly affects the sacrifice: success is most likely if the opponents are vulnerable but the sacrificing side is not.
However, if it turns out that the sacrificing side misjudged, and that the opponents' contract was unmakeable (or unlikely to make), the sacrifice is referred to as a false or phantom one.
A false sacrifice can cost heavily, as the sacrificing side has in effect turned a small plus into a (potentially large) minus score.
Kit Woolsey suggests that the following three conditions should all be met for a sacrifice to make sense in Matchpoint scoring: