[Gerben42]

When to open the bidding is a very complex game-theoretical question. For every system and style you can measure several things, for example:

* What is your average opening level?
* How much distribution do you show on average?

Things like that. Let's start with the 2nd question. Showing distribution is important. Playing a system that looks like the following is bad:

1♣ 10 - 12
1♦ 13 - 15
1♥ 16 - 18
1♠ 19 - 21
1NT 22+
rest preempts

More distribution-showing bids is a good thing.

What about average opening. If your average opening bid is higher you trade preemption for precision, sometimes in combination with losing distributional constraints. A simple one: Acol and SAYC.

In Acol, 1♠ shows only 4 cards but is opened more often than in SAYC. On the other hand 1♣ promises 4 cards also (but will be 5 most of the time if you open 4♣ 4M with 1M!).

Disadvantage: Less precise continuations after 1♠.
Advantage: More often you start with quite annoying auctions from opponent's point of view.

Same thing with minimum opening bids. Roth-Stone style is very precise when it comes up, but Pass is a frequent call and badly defined (also does not show distribution, see my 2nd point). Agressive openings get lots of distribution and preemption, but less precise follow-up bidding. The region in the middle is a bit of both. Pick your style

[csdenmark]

hrothgar, on Nov 24 2006, 06:44 PM, said:

csdenmark, on Nov 24 2006, 06:58 PM, said:

hrothgar, on Nov 24 2006, 04:35 PM, said:

>In my book by Slawinski/Ruminski "Introduction to weak opening systems" they
>are operating with a term called 'aggressiveness'. Anybody who knows what that
>term means?

The mean opening for a bidding system descibes the expected bidding level for the opening structure.  Each opening bid in the system is represented by two numbers.

1.  The number of steps of bidding space used (Pass = , 1♣ = 1, 1♦ = 2, ...)
2.  The frequency of the opening bid.  (pass occurs on 32% of all hands, 1♣ on 15% of all hands, 1♦ on 11% of all hands, ...)

Multiply the frequency of any opening by the number of steps of bidding space and sum across all openings.  If one assumes that all preemptive openings are equally difficult to defend against the metric provides a decent description of the preemptive effect of the bidding system.

Sorry Richard I dont understand much of that.

I'll try to give you a very simple example.

Lets assume that you play a very simple system that only used 4 opening bids.

30% of all hands that you get dealt are suitable for a Pass
20% of all hands that you get dealt are opened 1♣
10% of all hands that you get dalt at opened 1♦
30% of all hands that you get dealt are opened 2♦
10% of all hands that you get dealt are opened 2NT

The average open level for the system can be calcualted as follows

Pass used zero stepss of bidding space
1♣ uses 1 step of bidding space
1♦ uses 2 steps of bidding space
2♦ uses 7 steps of bidding space
2N uses 10 steps of bidding space

The average opening level =

.3 * 0 +
.2 * 1 +
.1 * 2 +
.3 * 7 +
.1 * 10

= .2 + .2 + 2.1 + 1 = 3.6

I see - thank you very much. I think I now understand the logic in this.

Seems like the estimate depends of the frequency of each opening used. Such must be dependent of the system and I assume those percentages(20% of all hands that you get dealt are opened 1♣) cannot be looked up anywhere - or?

The percentage for 1♣ in SAYC and in Regres I assume will be very different. Are such assumptions based on something? Empiri? Wishthinking? Tables?

Looks like Gerben has drawn attention to something here. The meaning of the bid in question. Then it is no longer only about the frequency.

[Gerben42]

You can calculate them simply by defining the bids. For example you can calculate that the chance to get a 15 - 17 NT is about half that of a 12 - 14 NT. In Acol you open 1M more often than 1m, in SAYC the other way around.

[jikl]

I think you'll find you open 1m more than 1M in Acol as 4 card suits are bid up the line.

Sean

[awm]

Let me try to summarize some reasons to open:

(1) In order to reach the best contract, when this contract is played by our side.
(2) To reach a good sacrifice (the par spot) when that is a sacrifice by our side.
(3) To help partner judge when to double if/when the opponents decide to bid.
(4) To indicate a lead in case we end up defending.
(5) To take up space and make it difficult for opponents to judge the par spot.

Here are some reasons not to open:

(1) Opening may expose you to a penalty for more than opponents can score on their own.
(2) Opening may cause partner to mis-judge (if openings are too wide ranging).
(3) Opening may give the opponents information which they can subsequently use in the play.

Looking at these guidelines, one can draw the following conclusions:

(1) It makes sense to open with better hands, since the best contract is more likely to be ours.
(2) It makes sense to be more aggressive with shapely hands including a major, because par is more likely to belong to us.
(3) It makes sense to be least aggressive with balanced hands.

Of course a lot of this will depend on system. The issue is that openings which are very wide-ranging in terms of strength and/or shape make it harder for partner to judge correctly. This means partner will often go wrong (case 2 under reasons not to open) and also makes opening less useful for reasons 3-5 (if you could have an awful hand, it's hard for partner to know to double, and if you could open a four small suit frequently the lead directing value is reduced, and if you open three-card suits with impunity then partner will often be unable to preempt).

Systems like SAYC and 2/1 GF emphasize a constructive approach. The primary reason to open at the one-level is to reach a game or slam played by our side. Openings are quite sound, helping partner to double and/or bid games. Of course there are certainly hands which could be profitably opened (mostly because of preemptive advantages 2 and 5) which these systems require you to pass because opening them within the system constraints will make it too hard for partner to judge other situations correctly.

Other systems often tend to be more aggressive, especially strong club systems like Moscito. The idea is that partner's judgement is not too impaired because of the lower upper-limit (openings are still fairly tightly described) and that the advantages from being able to preempt with these hands counter the disadvantages of giving information to the opponents on hands that belong to them and making it harder for partner to double in competitive situations when opener has "real" values.

[hrothgar]

csdenmark, on Nov 24 2006, 09:41 PM, said:

Seems like the estimate depends of the frequency of each opening used. Such must be dependent of the system and I assume those percentages(20% of all hands that you get dealt are opened 1♣) cannot be looked up anywhere - or?

I know two ways to derive frequency statistics for different bidding systems

1. Keep very careful records when you play. If you play enough hands, you'll eventually get reasonable estimates

2. Write a set of scripts that describe your opening style and feed these into a dealer program

[csdenmark]

hrothgar, on Nov 24 2006, 09:21 PM, said:

csdenmark, on Nov 24 2006, 09:41 PM, said:

Seems like the estimate depends of the frequency of each opening used. Such must be dependent of the system and I assume those percentages(20% of all hands that you get dealt are opened 1♣) cannot be looked up anywhere - or?

I know two ways to derive frequency statistics for different bidding systems

1. Keep very careful records when you play. If you play enough hands, you'll eventually get reasonable estimates

2. Write a set of scripts that describe your opening style and feed these into a dealer program

I doubt any of those options available 30-40 years ago.

What to say? The estimates for the polish pass systems are fairly arbitrarian and more based on the polish youngsters engagement than anything else. Such can be used for very little I think. Looks not to be able to predict anything of importance.

It is advised Antidelta with aggressiveness 2.32 to be used as a 1-2 seat opening system and Delta with agressiveness 1.8 to be used after pass-opening as response structure.

[csdenmark]

awm, on Nov 24 2006, 09:14 PM, said:

Let me try to summarize some reasons to open:

(1) In order to reach the best contract, when this contract is played by our side.
(2) To reach a good sacrifice (the par spot) when that is a sacrifice by our side.
(3) To help partner judge when to double if/when the opponents decide to bid.
(4) To indicate a lead in case we end up defending.
(5) To take up space and make it difficult for opponents to judge the par spot.

I think your arguments need to carry weights. They are not equally important.

I think (4) To indicate a lead in case we end up defending is of no really importance at this stage.

I think you are missing the point of pushing opps. into less precise defensive bidding. This is one of several points in playing strong pass systems. Strong Pass players take the upper hand unless opps. open in 1st seat. I think this is why the weak(0-7HcP) openings are not so dangerous as they looks like.

[hrothgar]

>>I know two ways to derive frequency statistics for different bidding systems

>>1. Keep very careful records when you play. If you play enough hands, you'll
>>eventually get reasonable estimates

>>2. Write a set of scripts that describe your opening style and feed these into a dealer >>program

>I doubt any of those options available 30-40 years ago.

Maybe they just sat down with a deck of cards and dealt out 10,000 hands over the course of a long weekend. Hell, if the definition of your openings is simple enough, you can always solve the problem by hand.

For whats its worth, I do know that 30 odd years ago I had access to DEC mainframes through my father's University. Admittedly, computing power was a lot cheaper here in the US than in Poland. At the same time, I could get a batch job run when I was a 10 year old kid. Hell, the TRS-80 first started shipping 29 years ago. I'm quite sure that you could run the necessary programs on that...

[Winstonm]

My thoughts are this: you should open the hand if the hand qualifies from previous agreements with partner about what constitutes an opening hand - and this discussion should be fairly deep into shapes, HCPs, interior spots, and doubleton honor combinations. It is not so important what you agree but that you agree as long as the agreement is honored within shades of judgement.

There shouldn't be a great deal of variance from an expected minimum.

[MarceldB]

Claus wrote:
>Seems like the estimate depends of the frequency of each opening used. Such must be >dependent of the system and I assume those percentages(20% of all hands that you get dealt >are opened 1C) cannot be looked up anywhere - or?
>The percentage for 1C in SAYC and in Regres I assume will be very different. Are such >assumptions based on something? Empiri? Wishthinking? Tables?

Underneath for the system DELTA you mentioned, the working-out of the figures

Pass:13+p. = 26,79%
1D: 0-7p. = 28,58%
1C, 1H and further: 8-12 = 44,63%

Pass , automatically : 0

1C, all balanced: 4333 up to 7222 = 64,3592% of the handshapes
x 44,63= 28,7056 x step 1= 0,2870

1D= 28,58 x step 2 = 0,5716

1H= s/v S most common 4441 up to 7330 = 32,83% of the handshapes
divided by 4 (s/v S only) = 8,2075% x 44,63 = 3,663 x step 3 = 0,1099

1S= s/v H , same--> 3,663 x step 4 = 0,1465

1NT= s/v D, 5c Major (so no 4441), = 0,094

etc. up to 2NT for the most common s/v shapes

-----
total:
Pas = 0
1C= 0,2870
1D= 0,5716
1H=0,1099
1S= 0,1465
1NT= 0,0940
2C= 0,1000
2D= 0,1237
2H=0,0500
2S= 0,0640
2NT= 0,010
3C and higher = 0,2694
Totally: 1,8261

Slawinski counted approx. 1,8

=====
I hope to have made it clear for you

regards,
Marcel