The club runs a number of competitions throughout the year and different scoring methods are used. This note explains the different methods and how your tactics should change depending on the scoring used.
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You score each board at your table in the normal way. Then this score is ranked against everyone else who played this board in the same direction: you score 2 matchpoints for every pair you beat and 1 matchpoint for every pair that you tie with. This gives a matchpoint score for the board. Your final score is the total number of matchpoints you score over the evening, normally expressed as a percentage.
The key in matchpoints is to beat the other pairs. It does not matter how much you beat them by.
NS 
EW 
Contract 
By 
Tricks 
NS+ 
NS 
Match points NS 
Match points EW 
1 
11 
1NT 
N 
8 
120 

6 
0 
2 
12 
1NT 
N 
7 
90 

3 
3 
3 
13 
1NT 
N 
7 
90 

3 
3 
4 
14 
3NT 
N 
8 

50 
0 
6 
For example, suppose there are 4 tables and you play one notrump making 8 tricks for +120. This score will be compared with the 3 other results, so the top on the board is 6 matchpoints if you beat everyone else. The bottom on the board is 0 matchpoints, when everyone does better than you! If everyone else makes 8 tricks in 1NT, then you will score 3 matchpoints (known as an average).
What will normally happen is that most pairs will play 1NT, making a different number of overtricks. If the other tables make it exactly, they will score +90 and you will beat all them. See how important overtricks are  your overtrick in 1NT has doubled your score on the board! Also note that you would have scored the same number of matchpoints if you had scored +1100  winning is important, not the size of victory.
The key tactic in matchpoints is to bid conservatively but play and defend well. A plus score rarely does badly at matchpoints. Overtricks are very important. Do not bid games or slams aggressively.
Every board is as valuable at matchpoints. If you play 25 boards, then each board is worth 4% of the final result. Part score hands and game hands are equally important. Making an overtrick in one notrump may be worth more matchpoints than bidding and making a grand slam!
In aggregate scoring, it does not matter what anyone else scores on a board. In matchpoint scoring, your result is compared with every other table. In IMP scoring, your result is compared with one other table, the table where your team mates played the board. The results at all other tables are irrelevant.
The team score on a board is determined by adding the two table scores together and this result is converted to International Match Points (IMP). For example, a difference of 30 points will be converted to 1 IMP. The reason for this is to reduce the impact of a single big swing, for example if you lost 1100 on a board it would be a disaster at aggregate scoring.
The team's result is the sum of all the individual boards and this will give you a IMP score for comparison with everyone else.
For example, suppose your opponents bid three spades but make ten tricks, you will score 170. Luckily your team mates bid four spades and also make ten tricks, so with the vulnerable game bonus this scores +620. Your team score is 170+620 = 450 points which converts to +10 IMP. However suppose your team mates bid four spades but only made nine tricks, for 100. Now your team score is 170100 = 270 points, which converts to 7 IMP.
This comparison suggests the tactics. If they make 10 tricks half of the time, then they will score +10 as opposed to 7, so you should bid games aggressively when vulnerable. Like aggregate scoring, overtricks are not really important, it is bidding games that is worthwhile. Unlike matchpoints, some boards will be more important than others.
Aggression is less worthwhile when you are nonvulnerable. So suppose your opponents bid three spades but make ten tricks, you will score 170. Luckily your team mates bid four spades and also make ten tricks, so with the nonvulnerable game bonus this scores +420. Your team score is 170+420 = 250 points which converts to +6 IMP. However suppose your team mates bid four spades but only made nine tricks, for 50. Now your team score is 17050 = 220 points, which converts to 6 IMP. So if the game is on a finesse, a 5050 chance, the odds are that you will win as much as you lose. So there is less need to bid aggressively.
Cross IMP scoring is teams scoring for pairs. It is a method that has only become popular with computer scoring since the calculations are extensive, but the strategy is exactly the same as IMP teams and aggregate scoring. Bid your games aggressively, beat the opponent's contract, overtricks are not important.
In teams scoring, you just score up with your team mates. In Cross IMP scoring, you score up with everyone else in the opposite direction, and then take the average of those scores. You can see why a computer is needed!
For example, suppose there are three tables and the scores on board 1 are:
Table 1: NS make ten tricks in four hearts for +420
Table 2: NS make ten tricks in three hearts for +170
Table 3: EW sacrifice in four spades doubled and make eight tricks for +300 to NS.
NS 1 compare first with table 2: +420 – 170 = +250 = +6 IMP
Then NS with table 3: +420 – 300 = +100 = +3 IMP
So NS 1 score the average of +4.5 IMP on this board and EW 1 will score 4.5 IMP
The table 2 NS will score up similarly.
First with NS 1: +170 – 420 = 250 = 6 IMP
Then with NS 3: +170 – 300 = 130 = 4 IMP
So NS 2 will score 5 IMP on this board and EW 2 will score +5 IMP.
The calculations for table 3 NS have already been done: they are 3 IMP with table 1 and +4 IMP with table 2, so NS 3 will score +0.5 IMP and EW 3 will score 0.5 IMP.
Also known as Total Points, you score each board at your table in the normal way. At the end of the evening, all your scores are summed together, both plus and minus scores, to give you a simple total. This is compared with everyone else and the highest score wins. There are two winners, one NorthSouth and one EastWest, because it would be unfair to compare the two directions as they did not have the same hands.
It is only your total score that is compared, not the individual scores on each board. This is the fundamental difference with aggregate scoring – it is only the total that counts.
The tactic for aggregate scoring is to get game and slam bonuses and defeat the opponent's contracts. Hands where you can bid and make game are very important. Overtricks are not very important because the difference between +110 and +140 is relatively small compared to the 300/500 game bonus. This means that you should bid games aggressively and take risks to defeat contracts. Get your bonuses and prevent the opposition getting them.
Overtricks are only important at matchpoints
If you have a close decision whether to bid game or not
If anyone wants to see the mathematical principles underlying this, just drop Paul an email.