Similar to the Monty Hall problem, but trickier: at the latest Gathering 4 Gardner, Gary Foshee asked
I have two children. One is a boy born on a Tuesday. What is the probability I have two boys?
We are assuming that births are equally distributed during the week, that every child is a boy or girl with probability 1/2, and that there is no dependence relation between sex and day of birth.
His Answer: 13/27. This was in the news a lot recently, see for instance BBC News. (Later analysis showed the answer depends on why the parent said that.)
