On 30 Jun 2014 at 16:09, Dan Asimov wrote:
Given a jar holding N marbles of each of C colors: --------------------------------------------------
I'm guessing the intended problem is either
----- I) Let f(r) be the probability that, after r marbles are removed one by one at random, there remain at least one marble of each color.
II) Remove marbles one by one until the jar first fails to contain at least one marble of each color. Let the random variable X be that number. (Or if you prefer, that number minus 1.) What is E(X) ? -----
Alas, I didn't realize I had proposed something so ambiguous. You are picking marbles and the question my wife was curious about was how many you would have to pick to have a p=.5 chance that _YOU_ hold at least one of each color. I figured that you probably need to calculate P(n) = probability that your handful of marbles includes at least one of each color after you've taking n marbles. And then solve for P(n) ~ .5 /B\ -- Bernie Cosell Fantasy Farm Fibers mailto:bernie@fantasyfarm.com Pearisburg, VA --> Too many people, too few sheep <--