Let's assume you are missing the Qxxx in a suit and you have AJ9xx in your hand and KT8x in the dummy.
- The first case is if you have absolutely no knowledge of who has what. If you try harder you may be able to find more information by playing other suits first. But let's say this is trump and you must draw trump first. What should you do. Playing the drop of the Q is 2% better then finessing. You can lead from either hand and it dose not make any different. If you are like me who have bad memory and how can you use logic to remind yourself of this? Usually here is how I think. You play the first trick and everyone follows. Then you play low towards the A/K and the opponent play low. Here is when you must think. In this case there is only two possibilities. There is only one card left which is the queen. Logic says at this time it is a 50/50 situation. Actually it is about 52.16% in favor of dropping the Q (see simulation result). With such a small % difference in the line of play like 2% it is usually better to use other factors. Think about other suit length and high card points. In our case here there is no more information and if you finesse you just took a line of play with 2% inferior then the drop.
- The second case is LHO has make a preemptive overcall of say 3C over your 1H bid. This does give you a lot of information on your heart play. Let's make it easy and say LHO lead the club K and everyone follows and win it with the club A and you have 3 clubs in each hand. At this point there is about 99% chance LHO has KQJxxx in club and RHO has x in club. This means RHO must have 5 more cards in the other suit. Simple logic say it has 5/3 = 1.67 more cards in each suit. Thus the RHO must have more chance to have long hearts then the LHO. So the correct line of play is J from the hand to the dummy's K. If everyone play low play a heart toward your hand. So far so good. do you play for the drop or play for the finesse? Computer simulation say 57% chance for finesse to work.
- The third case is LHO has make a simple overcall of 2C over your 1H bid. This does give you some information on your heart play. The 2c bid say that player is more likely to have short heart. Let's use the same scenario as the second case and a club is lead and you won with the A and you have 3 clubs in each hand. Since RHO has better chance to have more hearts you play from your hand the J to the dummy. If everyone play low you lead the T from the dummy to your A. RHO play low. Now do you drop or finesse? Computer simulation say only 48% chance for the finesse, different than the previous case. The major difference in the two cases is that in the second case LHO has a good chance of only 5 clubs and not 6.That changes the % drastically.