IMP Pairs FAQ
What is it all about and why do we do it?
1. How is IMP Pairs scored?
2. What are the advantages?
3. What are the disadvantages?
4. Never mind that, why are we doing it?
5. How should we adjust our game with this sort of scoring?
6. I've heard of the "Butler Method". Is that the same thing?
1. How is IMP Pairs scored?
The score at your table is compared to the score at every other table and the result
converted to IMPs just as if each were a team match. These numbers are added up and then
divided by the number of comparisons made (this division has to take place because often
some boards are not played the same number of times). This gives you your average IMPs
compared to all other tables. These numbers are added up for the whole session - which gives
each pair what you might call thier 'raw IMPs score'. Finally, as some pairs may not have
played the same number of boards as everyone else, the pairs who have played less boards get
their score multiplied by an appropriate amount to bring their score into line. This is
called the "Cross IMPs method".
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2. What are the advantages?
a. IMP scoring is more like 'real bridge' in that making your contract,
especially games and slams gets a suitable reward, whereas the few
points for an overtrick are almost irrelevant.
b. There is little to choose between 3NT and 4 of a major and the few
points difference is almost irrelevant, so you should choose the safer
game, the same as if you were playing rubber bridge.
c. At normal pairs scoring (matchpoints), pairs have a natural fear of
going past 3NT in search of a minor suit slam. This has the effect of
making people's slam bidding rather poor. As 5 of a minor will score OK
compared to 3NT at IMP scoring, your slam bidding should improve.
d. Safety plays that risk not getting an overtrick in return for greater
safety are a luxury that you (usually) cannot afford at matchpoints.
Yet a lot of bridge literature is about this very topic and may well
have figured significantly in any lessons on the game you may have
taken. It is nice, at least for a change, to have a form of scoring
where safety plays may figure more prominently.
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3. What are the disadvantages?
a. Matchpoint bridge may not be 'real bridge', but it is no less
exciting, with tactics all of its own.
b. Matchpoints are simple to score and simple for everyone to see where
their score has come from.
c. At matchpoints, as each board is worth a simple top, bottom or a
shade of grey in between, over a limited number of boards (and 27 is
limited), you may get a fairer result (fairer in the sense of less
random) as each board is worth the same amount. If a good pair comes to
your table and bids a slam that the rest of the room has not been able to
find, you will get a bottom at matchpoints which may be no fault of your
own. This is an unfortunate setback, but because each board is worth the
same as every other one, you can potentially recover on the next (perhaps
partscore) board. At IMP scoring you will need at least two, probably
three partscore swings in your favour to make up the lost ground. This is
not a concern in the long run (luck will even itself out), but in a single
session at IMP scoring a few 'big boards' has a bigger effect than at
matchpoints.
This is probably the main reason why matchpoints should be the norm for
pairs scoring for most sessions - though it is not a compelling reason
why all sessions should be scored that way.
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4. Never mind that, why are we doing it?
Well, apart from the things listed above as advantages of IMP scoring,
the actual history goes back to the 5th Monday of the month when we had
'random teams'. Some did not like teams because they did not like
depending on (or being depended on by) another pair. And those that did
like teams didn't always get what they wanted when we ended up with an
odd number of pairs and therefore could not play proper teams. IMP
pairs seems like an ideal compromise. We've extended it to some eight
first fridays as well in order to provide those that play on Fridays but
not Mondays a similar opportunity. As a result of this we now have an
IMP pairs ladder competition running on the web.
Additionally, there are those who play team matches outside the club
sometimes, but, as nearly all bridge is pairs (and therefore
matchpoints), there is actually very little opportunity to practice the
tactics required for team matches. Playing at least some sessions of
IMP pairs provides that opportunity.
Also it is a bit of variety. We do as many different forms of
competition as we can over the course of the year in order to try to
give something to everyone. IMP pairs is just part of that overall
effort.
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5. How should we adjust our game with this sort of scoring?
You could write a book about this, but briefly:
a. When choosing which game to be in, you should choose the safer
option.
b. You should not fear being in 5 of a minor so much as you do at
matchpoints, especially if you want to investigate the possibility of
slam.
c. If you think your side has the majority of the points, but not a
game, then the opponents bid over you, you're in a situation where you
will need to think if you should bid one more yourself, double the
opponents or just pass. This is a very common situation. Often at
matchpoints you should double and pass is commonly the wrong answer. The
reason is simple enough - if the opponents can make their contract
you're getting a poor score anyway, so the extras they get for making a
doubled contract won't hurt you very much, if at all. Whereas an extra
50 or 100 if you can get them off may make quite a difference to your
matchpoint score. At IMPs the maths is a little different - the extras
they get for making a doubled contract, particularly if you double them
into game, will hurt you badly. And, if they're off, the extra 50 or 100
won't benefit you very much. In any case, at IMPs, if it is a partscore
board that your side should be getting a plus for, it will, at least, not
be a bad board for you if you collect any sort of plus at all.
d. At matchpoints, if you have a close decision between bidding game or
not, then it is generally right to be conservative in your approach.
The reason is simple, if the game turns out to be worse than a 50/50 bet
then the advantage of staying low is obvious. And if it is a 50/50 bet
then, by staying in the partscore, you will still pick up a few
matchpoints from those who have got into the wrong denomination (which
is more common than one might think), provided, of course, that you
don't get too high yourself. At IMP scoring the game bonus is worth
pursuing especially vulnerable and you should be more aggressive in your
game bidding (marginally).
e. At IMP scoring generally you should play to ensure your contract as
overtricks are of little value. And in defence you should play to get
the contract off even if this risks giving away an overtrick.
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6. I've heard of the "Butler Method". Is that the same thing?
Yes and no. The Cross IMPs method is pretty much an unthinkable way of scoring by hand,
but there is a simpler way of doing it that gives quite comparable results which could be
done without a computer called the Butler Method. To do this you throw out the top and
bottom score for each board (they might be quite freakish) and average the rest. This
score is rounded to the neartest 10 (so it looks like a real bridge score, even if it isn't).
This number is called the "datum" and your result is calculated by taking your result and
comparing it to the datum and scoring by IMPs. Your score on each board is added up for the
session and, as with the Cross IMPs method, pairs who have played less boards get their final
score adjusted by an appropriate factor to allow for this.
The two principle advantages of the Butler Method are:
a. It is easier to do by hand (but this is irrelevant if you have a computer to score as
we do)
b. It is rather easier to see where your score has come from (as the final traveller seen
on the web normally has the "datum" shown).
The principle disavantages are:
a. The scores for North/South and East/West are not guaranteed to sum to zero, which is
particularly of concern if it is a one winner movement.
b. Without going into technical details, you can get anomalous things happening, if, for
example, the director adjusts your score. Cases have been known where your score goes up
but your IMPs go down.
In practice there is little difference between the two. We use the Cross IMPs method as it
technically the superior choice given computer scoring.