A 7 4
K J 6 5 2
Most players realize that, initially the queen is more likely to be the hand with three cards rather than the hand with two, but after they have played ace and another, and the queen has not appeared, they tend to review the situation.
At this moment there are only two cards outstanding and it is tempting to suppose that the card held on the left (assuming a 3-2 break) is as likely to be the queen as a low card. Thus it may seen as reasonable to play for the drop as to finesse.
There is a fallacy in this line of argument, as can readily be seen if the example is transferred to a different setting. Suppose you hold four copper coins and one silver coin and you distribute at random two coins to West and three to East.
At this moment, obviously, East is more likely to hold the silver coin. Now if You demand one coin from West, two from East, stipulating always that the silver coin is not to be freely given up, the probabilities must remain the same. In short, the finesse is still the better play.
There are, nevertheless, many occasions where it si right to spurn the finesse for tatical reasons. This is a fairly simple example.
7 4 2 10 9 K 8 5 A K J 8 6 | ||
A J 8 6 K J 4 A Q 4 10 9 4 |
7 4 2 10 9 K 8 5 A K J 8 6 | ||
5 3 A Q 7 6 5 9 6 3 7 5 3 | K Q 10 9 8 3 2 J 10 7 2 Q 2 | |
A J 8 6 K J 4 A Q 4 10 9 4 |