[Bbradley62]

This is irrelevant in the actual auction, but could be relevant on other hands. None vul, North dealer, the auction is:
P -(P)-1♠-(P)
2♠-(3H)-?
The possible 3S is explained as 6+S; 12-15 total points.
Why 6+S? Can't I be competing with 5S and 14?
The possible 4S is explained as 18-22 total points.
Shouldn't one or the other include 16-17?

[barmar]

GIB's competitive bidding is mostly based on the LOTT, which explains why 3♠ should show 6+.

There's no 16-17 because the interference has taken away the space for invitation. This is the problem that Maximal Overcall Doubles were designed to address, but GIB doesn't use this convention.

[Bbradley62]

barmar, on Sep 10 2010, 12:56 AM, said:

There's no 16-17 because the interference has taken away the space for invitation.

Has the interference eliminated the possibility that I hold 16-17 points and want to bid more spades? The 12-15 and 18-22 ranges should be adjusted to include 16 and 17.

[arigreen]

Not playing maximal doubles, GIB's ranges here seem pretty reasonable to me. 3S is competitive (less than invitational values) and 4S is to play (game going values). (Yes, 4S could be an advance sacrifice but most of the time it isn't.) With invitational values GIB simply has to choose which bid to make, so it will probably simulate. Sometimes it will bid 3S and sometimes it will bid 4S. However, it is important that the description for 3S not include hands with up to 17 points -- if it did, then partner-GIB would often raise 3S to 4.

It would not be terrible if the description of 4S were changed to "16-22 total points" even though not all hands with 16 total points bid 4S. Still, I think this is a bit of a misdescription since many hands with 16 total points will not bid 4S.

In any case, GIB is instructed never to bid again over opener's 4S rebid in this particular auction. As a result, it doesn't matter so much what the precise description of 4S is.