# General Approach to the Cube, by John O’Hagan

When to double in a match is a difficult question to answer.  There’s no one magic formula that will always give you the right answer.  The idea is to maximize your MWC (Match Winning Chances).  To figure that out though can be extremely difficult at times.

Generally, the less efficient your double, the more volatile the position has to be.  So if you’re just barely in your doubling window, doubling is probably only correct if there are a lot of big market losers on tap.

If it’s a NMS (Normal Match Score–meaning the take points and gammon values are close to money), just treat it like money.  If you are within 4-5% of the opponent’s takepoint then you probably have a double if you can find 9/36 market losers, provided the non-market losers are not killers.

Also remember Lamford’s rules:  With the cube in the middle, add 1/6 of the difference between the 2 sides winning chances i.e. 59-41 becomes 62-38.  If the cube’s been turned, cube ownership adds 1/6 to the cube owner’s cubeless chances i.e. someone owning the cube with 30% cubeless chances has about 35% cubeful chances.

Ex, a money game or NMS.  A medium length race with the leader having 70% cubeless chances.  1)Should he double?  2)If he owns the cube should he redouble?

Should he double?  If he doesn’t double, his 70/30 edge in the game should translate into about a 77/23 cubeful favorite.  So if he doesn’t double now, his equity is about .54 points per game (arrived at as follows 77-23/100).  If he does double and the oppt correctly takes, he’s about a 65/35 cubeful favorite (the oppt will own the cube so his chances increase from 30% to 35%).  If he doubles, his equity is about .6 points per game ( 65-35/100 x 2), so doubling is correct.

How about redoubling?  If he doesn’t redouble, cube ownership should change his winning chances from 70/30 to about 82/18.  His equity will then be .64 x 2 points per game = 1.28 points per game (82-18/100 x 2 since the cube’s on 2).  If he does redouble and the oppt takes, his 70/30 cubeless advantage is lowered to 65/35 so his equity is .3 x 4 points per game = 1.20 points per game (65-35/100 x 4 since the cube is on 4).  So redoubling costs -.08 points per game and it’s better to hold the cube.