[mpefritz]

As I've posted before on the Monty Hall problem set, the choice to change curtains depends on HIS strategy for opening an empty curtain (goat curtain).

In the text of the book, I believe they state that the expected length of an opening lead from a longest suit (key assumption which is often NOT appropriate) is 4.5 cards. Therefore, if a 4 card suit is led, then there is some new information. especially if you assume that they would randomly lead from either of 2 4-card suits. (Just like Monty hall would "randomly" choose to open either of 2 unchosen goat curtains....)

In the example given, it clearly depends on partnership leading style, or whether a 4 card major would be led first dogmatically, or whether the leader has enough HCP on the auction to try to set up one of his sits, or whether the lead is made to set up partner's suit.

I'd play for the club queen with West and get yelled at by partner.

fritz

[1eyedjack]

JRG, on Aug 23 2004, 11:21 PM, said:

The fact that he leads his longest suit does not really tell you much (I would agree that if he leads from a 7-card suit, it does tell you something)

I note that if you transfer one or more known cards from one defender to the other defender the difference between their vacant spaces is double the number of cards transferred. For example, if you test a side suit and it is 3-3, then their vacant spaces may be computed on that basis. But if the test showed that the suit broke 4-2 (a transfer of one card between the defenders in that suit) then the difference between their respective vacant spaces changes by two for each one card transferred (compared with the 3-3 alternative).

So I was wondering: If the Spade lead is expected to be from a 5 card suit (I approximate to that from the theoretical 4.5), upon which confirmation you have no new data to calculate your vacant spaces, but you accept that you HAVE additional information if instead it turns out to be from a 7 card suit (2 more than expected), then the question arises: If you wish to use vacant spaces analysis for the second scenario (ie the 7-0 break), should you

(1) treat the void hand as having 7 more vacant spaces than his partner, or
(2) treat the void hand as having 4 more vacant spaces than his partner (being double the difference between a void and an expected doubleton), or
(3) something else (specify)
?

[dogsbreath]

hi all ..
I'd like to know what level of player the West player is .. if a good player then the lead is a little unexpected on the bidding .. and we have 8cards missing in both majors..but no major lead. If West is a good player there is an inference that he has AT LEAST 4 diamonds and most of the missing honour cards.. explaining lack of major lead since not expecting p to have an entry. (Also why i suggest maybe 5 diamonds.. no harm in misleading p if he has no entry)
..Or maybe it's board 63 of the match, W is tired and led 4th best robotically.
Dogs think of these things you know
Rgds

Quote

furnulum pani nolo

[JRG]

mpefritz, on Aug 24 2004, 05:45 AM, said:

As I've posted before on the Monty Hall problem set, the choice to change curtains depends on HIS strategy for opening an empty curtain (goat curtain).

In the text of the book, I believe they state that the expected length of an opening lead from a longest suit (key assumption which is often NOT appropriate) is 4.5 cards.  Therefore, if a 4 card suit is led, then there is some new information.  especially if you assume that they would randomly lead from either of 2 4-card suits.  (Just like Monty hall would "randomly" choose to open either of 2 unchosen goat curtains....)

In the example given, it clearly depends on partnership leading style, or whether a 4 card major would be led first dogmatically, or whether the leader has enough HCP on the auction to try to set up one of his sits, or whether the lead is made to set up partner's suit. 

I'd play for the club queen with West and get yelled at by partner.

fritz

Remember Bourke & Smith are not saying vacant spaces theory is wrong; just that you have to be very, very careful about using it based solely on the opening lead -- the information you get from the opening lead is not random. The convincing argument for me was to simply play the hand in the same contract from the other side of the table (when the deal - all four hands - is the same).

I think what most people are arguing in this thread is not using vacant spaces at all. This is essentially what Bourke & Smith do. At the risk of quoting too much from their book, they later go on to argue:

Go back to the first layout (when South became declarer). What if West had still led a spade but the suit had broken 4-3? West would still have nine unknown cards to East's ten, but in fact the true odds would favor playing West for the ♦Q. Why? Because West has presumably led his longest suit -- spades -- in which he has only four. West, therefore, does not have five hearts or five clubs and may well have no more than three of either suit. The only time he will have a singleton diamond is when he is precisely 4-4-1-4, and then might equally have chosen to lead from a four-card heart or club suit.
====

As you suggested, the precise arguement above might not hold, depending on opponents' leading style, but the general concept of treating the information from the opening lead as meaningful rather than random does.