Goren bridge: Know your percentages

Today’s deal illustrates why good players, or players who want to be good, invest some time into learning some of the basic bridge percentages. It is not that complicated, and it does not take a math ‘whiz’, it just takes a little time and effort. Any activity worth your time deserves a little effort.

East wins the opening trump lead with his ace and shifts to a low spade. West wins with the ace and shifts to a diamond. Should declarer take the diamond finesse or rise with the ace and hope for four tricks from the club suit? The chance for a successful diamond finesse is 50%. The chance for the six missing clubs to split 3-3 is 36%. So we should take the diamond finesse, right? Not so fast. There is also a chance for the doubleton jack of clubs to fall – an additional 16% chance. It’s a coin flip now. There is also an 8% chance that West will have five or more clubs, making a finesse for the jack a sure thing. That makes the club suit about a 60% chance to provide four tricks. Rise with the ace of diamonds!

Unless you want to go out and conquer the tournament world, knowing the exact percentages is not necessary. Rounding them off into numbers that are easy to remember will usually be enough.