The best way to understand IMP strategy is to look at the gains and losses for certain actions. You will learn which risks have worthwhile payoffs. I’ll present a few scenarios and we’ll compare your action and result to hypothetical opponents to see how much you gain or lose.
Situation: Bidding Vulnerable Games
Suppose you are trying to decide whether or not to bid 4H. Let’s look at your possible outcomes versus your actions.
If you make 4H vulnerable you score +620 . If you go down one trick you score _-100_ .
If you stop in a part score and make 10 tricks in H you score +170 . If you make 9 tricks you score +140.
Assume both sides make 10 tricks, but only one side bids the game. That side wins 10 IMPS.
Assume both sides make 9 tricks, but only one side bids the game. That side loses 6 IMPS.
You should bid a vulnerable game if you have about a 40 % chance or better of making it.
Situation: Bidding Non-vulnerable Games
Suppose you are trying to decide whether or not to bid 4H. Let’s look at your possible outcomes versus your actions.
If you make 4H non-vulnerable you score +420 . If you go down one trick you score -50 .
If you stop in a part score and make 10 tricks in H you score +170 . If you make 9 tricks you score +140.
Assume both sides make 10 tricks, but only one side bids the game. That side wins 6 IMPS.
Assume both sides make 9 tricks, but only one side bids the game. That side loses 5 IMPS.
You should bid a non-vulnerable game if you have about a 45 % chance or better of making it.
Situation: Doubling them Into Game
Suppose you are trying to decide whether or not to double their part score contract (assume 3H), where they will make a game if they make the contract.
If you set them 1 trick and they are vulnerable you score +200 . Set them two tricks and you score +500 .
If they make the contract you score -730 .
Assume you double the opponents in 3H while your teammates play the same contract undoubled, making the same number of tricks.
If you beat it two tricks vulnerable while your teammates go down 2 undoubled, you win 7 IMPS.
If you beat it one trick while your teammates go down 1, you win 3 IMPs.
If they make it doubled while your teammates make it undoubled, you lose 11 IMPs.
Bottom line: Don’t double if you’re just trying for a one trick set.