Probability is hard

There is a nice article on the ScienceNews.org site about the Tuesday birthday problem:

I have two children, one of whom is a boy born on a Tuesday.  What is the probability that I have two sons?

The article does a very good job of discussing the solution, as well as why it is difficult (and why "Tuesday" has anything to do with the solution).  Commenters have pointed out that there is an additional problem: what the meaning of "one of whom" is.  It could mean "at least one of whom," which is the strictly correct mathematical interpretation, or "exactly on of whom," which is what most people would read if they are not being careful. 

And we wonder why students hate word problems!  Problems like this are often offered as examples of how counter-intuitive probability (especially conditional probability) can be.  And probability can be counter-intuitive -- just see the Monty Hall Problem.  However, problems like these two children birthday paradoxes are often confusing mostly because of the wording.  We should be very careful to remove all ambiguity from the question and let the interesting mathematics stand on its own.