Cumulative probability question

*To*: mathgroup at smc.vnet.net*Subject*: [mg120583] Cumulative probability question*From*: Peter Sisak <p-kun80 at hotmail.com>*Date*: Sat, 30 Jul 2011 05:59:41 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

I have been experimenting with Mathematica in order to receive answers to my problem, so far without success. I have tried various forms of CDF and HypergeometricDistribution, but I seem to not know the proper addressing of the parameters for the problem. The problem itself is the following (with numbers given for a more illustrative example): Given an urn containing N(=70) items in total, of which n(=4) are marked, we want to draw i(=2) or more marked items. a) What is the formula describing the number of draws required to succeed in drawing at least i items with a probability of at least 50%? b) How do you make a graph of the probability (of drawing at least i items) graphed against the number of draws? c) What are the equations that need to be solved to get a numerical answer on a) and b)? Thank you for your assistance in advance P=E9ter Sis=E1k