An urn contains 4 white and 4 black balls. We randomly choose 4 balls without replacement (this constitutes one "trial"). If the result is 2 white and 2 black balls, we stop. If not, then the balls are replaced and the procedure is repeated until we obtain the desired result.
(a) Are the trials in this experiment independent? Explain.
(b) Use the Hypergeometric distribution to compute the probability of getting the desired result at a particular trial.
[NOTE: This is the "success" probability for part (c) ]
(c) Hence find the probability that exactly 3 trials are needed to get the desired result.