The most important general finding is that double dummy analysis is very accurate as compared to actual play from OKBridge. The overall total number of tricks taken by the declarer is 9.21 (9.22 for imp and 9.20 for mp).  The double dummy analysis of the same deal produce 9.11 (9.12 for imp and 9.11 for mp).  So actual play by OKBridge player takes 0.1 tricks more then the double dummy analysis result. This is based on 30 million plays on Okbridge. The following table is a break down of the numbers by the level of contract.                         actual play  double dummy    difference level 1        7.43      7.06      0.37 level 2        8.12      7.97      0.15 level 3        9.01      8.87      0.14 level 4        9.84      9.85     -0.01 level 5        10.12     10.07      0.06 small slam     11.42     11.51     -0.09 grand slam     12.05     12.14     -0.09 Any research done on bridge hands using double dummy analysis should be accurate enough for any bridge playing applications. If you want to be more precise you can make an adjustment of about -0.1 tricks for slam contracts and +0.15 tricks for level 2 and level 3 contracts. The double dummy number is the one for the denominations the declarer is in and not for the most tricks. For example the most tricks is in club and NS can make 9 tricks. But if the declarer is in NT and the double dummy analysis only gives 8 tricks, then 8 is used and not 9. So this is a measurement of how well the declarer play the hand and not how well the declarer bid the hand. The following table is a break down of the numbers by the level for NT contact.                         actual play  double dummy    difference level 1       7.34      6.93      0.41 level 2       7.86      7.56      0.30 level 3       9.29      9.10      0.19 level 4       10.25     10.10      0.15 level 5       10.34     10.25      0.09 level 6       11.40     11.48     -0.07 level 7       12.27     12.40     -0.12 This set of data clearly shows the deviation from +0.41 in 1NT to -0.12 in 7NT. The following table is a break down of the numbers by the level for spade contact.                         actual play  double dummy    difference level 1        7.83      7.64      0.19 level 1        8.18      8.06      0.13 level 1        8.61      8.52      0.09 level 1        9.86      9.87     -0.00 level 1        10.30     10.23      0.07 level 1        11.45     11.57     -0.11 level 1        12.26     12.39     -0.12