The formula tries to capture the following:
-
game prospects (working HCPs, seat)
-
preemptive value (bypassed suits)
-
lead direction
-
form of scoring, vulnerability and level
Furthermore, the formula only applies to direct, non-jump overcalls of
an opening bid. So even if the hand doesn't qualify, it could qualify
as a weak jump overcall or as a reopening overcall. However, the
rules for intervening after both opps have bid are not covered in the formula.
Finally, I realize that this formula is rather complex and unwieldy
for use at the table. Maybe I can somehow simplify it or make it
easier to remember. A computer would handle it well.
OK, enough preamble, here goes:
-
HCP evaluation. For my suit of at least five in length, use this
scale: A=5, K=4, Q=3, J=2, T=1. For their suit, use A=4, K=2.
For other suits: A=4, K=2, Q=1. As usual, reduce the count for non-offensive
honors (e.g. for Qx would count 0 in an "other" suit). When "my"
suit is only four-cards, just count normal 4321 for my suit, and subtract
a point for each other A.
-
Length evaluation. Add the following for length of "my" suit:
5: 1, 6: 2.5, 7: 4. If you believe Mike Lawrence in all matters,
then you can also add according to your length in "their" suit: 4: 1, 5:
2.
-
Preemption. For every suit your overcall bypasses, add for shortness
as follows: xx: 1, x: 2, void: 3.
-
Vulnerability, scoring and level. Whenever they are vulnerable, add
a point. Subtraction when we are vulnerable is calculated as follows:
1-level: MPs: 1.5, IMPs: 2. 2-level: MPs: 3, IMPs: 4.
If not vul, at 2-level. MPs: 2, IMPs: 3.
-
Miscellany: subtract 2 if pd has already passed. Add 1 if LHO
has already passed. Add 1 at MPs if our suit is the "boss" major
suit (e.g. 1H over 1D, 1S over 1H, but not 2H over 1S).
The "Magic" number is 11 (another "rule of 11"). If your hand scores
11, then you will probably make the overcall. 12 would be automatic.
10 says pass (or consider a weak jump overcall if appropriate).
Examples (these were not what I tested the formula on - so they are
new to me, too):
(p. 45 of Mike Lawrence's book - Ch 6: Quiz)
MPs, nv/nv, RHO deals and opens. You hold: AQJ8 42 AT865
83
RHO: 1D. score: 10+1+1+0+1=13 bid 1S.
clear-cut according to ML. At vul/nv score would be 11.5. At
IMPs vul/nv score would be 11 and I think I would pass. Not sure
about ML.
RHO: 1H. score for 1S: 10+0+0+0+1=11
ML: might work out.
RHO: 1H. score for 2D: 11+1+1-2+0=11
ML: dangerous
RHO: 1S. score for 2D: 10+2+1-2+0=11
ML: reasonable at MPs, almost acceptable at IMPs (would score 10).
(p. 47)
MPs, nv/nv. You hold 72 KQ865 K65 A42.
RHO: 1C or 1D. score for 1H: 13+1+0+0+1=15.
ML: 1H is easy at any game. If we were vul/nv, would still
score 13 at MPs, 12 at IMPs.
RHO: 1S. score for 2H: 13+1+0-4+0=10 ML:
a dangerous overcall at MPs which could easily be wrong. clear pass
at IMPs (score: 9).
(p. 48)
MPs, nv/vul. K62 J9763 4 AK87
RHO: 1C: 10+2+2+1+1=16 ML: 1H any vulnerability;
IMPs, too (score 13). The fit factor is overwhelming.
RHO: 1D: 10+1+0+1+1=13 ML: 1H.
but at vulnerable IMPs (score 10) best to pass
RHO: 1S: 10+1+0-1+0= 10 ML: pass.