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Slam bidding at IMPs

#1 User is offline   baabaa 

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Posted 2021-April-09, 15:22

I've struggled to find the answer to a rather simple question. About how often must a slam (small or grand) make for the bid to be profitable long term at IMP scoring?

If I understand the scoring correctly, a non-vulnerable game has to make about 50% of the time to break even, while a vulnerable game has to make about 40% of the time.

What about slams? If i understand correctly, they need to make more than 50% of the time?
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#2 User is online   smerriman 

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Posted 2021-April-09, 15:28

See here.

A non-vulnerable game is 45%, vulnerable game 38%, while the vulnerability doesn't matter for a small slam - major suit 50%, and minor suit 48%. Grands are more complex as they depend on how you think other tables will bid (as explained in detail there).
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#3 User is offline   thepossum 

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Posted 2021-April-09, 16:13

If you can work all that out in your head and realise that most of it is oversimplified and ignores all other considerations (as Stephen has mentioned) my rules for bidding slam are in no particular order

- if you think there is a good chance it will make
- if you just feel like bidding it anyway
- if you are having a bad match and its near the end of a session and you need to take risk
- how you feel your abilities stack up against the opposition - let them bid and fail and you make game etc
- etc
- etc

TBH I rarely go beyond simple rules on numbers of controls, losers, points, other features and a bit of gut feel or mood at the time

However as someone more at home in novice and beginner I feel a bit out of my depth even commenting here :)

EDIT This is an interesting and somewhat related analysis of historical slam bidding which I always find educational Kidd's analysis of slams
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#4 User is offline   DavidKok 

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Posted 2021-April-10, 04:14

My personal guidelines are that I want to bid small slams if they have more than 50% chance. I'm indifferent about slams that depend exactly on a finesse, but typically I stay out of them (and shrug if someone bids and makes it). For grand slams you want to be very sure what you're doing - I personally stick to around 70-80% as a rough indication (but this reflects the fact that my field has a tendency to miss good slams).
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#5 User is offline   paulg 

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Posted 2021-April-10, 05:15

View PostDavidKok, on 2021-April-10, 04:14, said:

I'm indifferent about slams that depend exactly on a finesse, but typically I stay out of them (and shrug if someone bids and makes it).

This is a good philosophy since most slams that "depend on a finesse" are worse than 50%, because we tend to ignore the possibilities of bad breaks. Although 5-0 and 6-0 breaks are rare, though still reducing our chances a little, everyone tends to ignore the problems of a 4-1 break in a suit which is far more common than most seem to appreciate.
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I don't work for BBO and any advice is based on my BBO experience over the decades
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#6 User is offline   pescetom 

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Posted 2021-April-10, 08:17

View Postpaulg, on 2021-April-10, 05:15, said:

Although 5-0 and 6-0 breaks are rare, though still reducing our chances a little, everyone tends to ignore the problems of a 4-1 break in a suit which is far more common than most seem to appreciate.

28% IIRC, indeed a lot more than one might guess.
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