Consider an urn 
, with 15 blue balls, and 10 red balls, and an urn 
, with 10 blue balls, and 15 red balls. We select randomly one urn (with probability 50% for each urn).
We draw a ball, which turns out to be blue, and we put it back in the urn, Now, we draw a (second) ball. What is the probability that this (second) ball is blue?
, with 15 blue balls, and 10 red balls, and an urn , with 10 blue balls, and 15 red balls. We select randomly one urn (with probability 50% for each urn).We draw a ball, which turns out to be blue, and we put it back in the urn, Now, we draw a (second) ball. What is the probability that this (second) ball is blue?
Solution after the break!
