Flavio wrote:

Furcifer wrote:

Flavio wrote:

Lots of backpedalling and excuse making that he wasn't thinking clearly when he printed the original (wrong) answer.

So he's claiming that when he asked the original question, he intended to imply that he would always report the existence of a daughter if there was at least one daughter in the family. It is plausible that this was his intent, but the original question doesn't make it clear.

Cecil wrote:

Granted the question is subtle. Consider: we are to be visited by the two kids just described, at least one of which is a girl. It's a matter of chance who arrives first. The first child enters--a girl. The second knocks. What are the odds it's a boy? Answer: 1 in 2. Paradoxical but true. (Thanks to Len Ragozin of New York City.)

What was subtle about the original question? Does he mean confusing as to whether "a daughter" means "at least one" or "only one"? Neither makes the answer two out of three.

The door example is correct, though there's nothing paradoxical about it.

For even more faulty logic and stupidly worded questions, check out the gameshow door problem in the first link.