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".
+++++
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.
+++++
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.
+++++
Well, apart from the things listed above as
advantages of IMP scoring, we tried random teams but 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 decided to run every third Wednesday for the time
being. We could have an IMP pairs ladder competition running on the
web.
Additionally, there are those who play team matches
outside the club sometimes or for the club in Essex competitions 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.
+++++
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.
+++++
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.