Dear R-users, Could any give me a guidence to solve the following problem? I have three balls A, B and C. I can pick A, B or C at the first selection. At the second and third selections, I can either (i) pick one of the remaining balls, or (ii) stop to pick any balls. Therefore, I have a classification table: 1st 2nd 3rd n A -- -- 9 B -- -- 3 C -- -- 5 A B -- 7 A C -- 1 B A -- 9 B C -- 2 C A -- 0 C B -- 3 A B C 5 A C B 6 B A C 8 B C A 9 C A B 3 C B A 2 My interest is on the estimation and test for the association between A and B. In a special case, what is the assocaition measure between A and B if the first pick is either A or B? Does anyone have done this kind of analysis? Thanks in advance. Han-Lin Lai