PhilKing, on 2012-November-28, 11:03, said:
We rise with the ace and claim ten tricks, obviously. We always make exactly ten trick when the club loses, hence 33.33%.
I think his figure for 11 tricks is basically 1/4 x 2/3 (16.66%) - ie the club finesse wins but West has both diamond honours, but higher against an overly aggressive leader.
There is a vacant spaces issue hence the word "roughly" followed by a decimal.
Thanks for elaborating correctly.
You just have to look at the correct line of play for each case once when you play for the drop and once for the finesse in clubs.
Usually this means taking the double finesse in diamonds, unless you took a failing club finesse and a diamond return, in which case you have to rise with the ace to discard your heart on the fourth club.
Approximate and roughly is also correctly explained. The true probabilities for restricted choice are not exactly two to one, lead considerations and vacant spaces have not been taken into account, but I believe the additional precision to be gained here looks rather small to me.
Rainer Herrmann