A cameraman working for a television company that films wildlife was out in the wilderness somewhere when he spotted a bear 1 mile to his east. Unfortunately the sun was in a bad position for filming, so he turned north and walked straight ahead for 1 mile. This little puzzle will be familiar to most of postgraduates – though probably in its less politically correct version in which the man shoots the bear. The point of this puzzle is to convince postgraduates that even in a subject as clear-cut as geometry, it is easy to make unwarranted assumptions. In the far more messy world of experimental science, it is even easier to make unwarranted assumptions. The elegant probability puzzle is about a game show. A simple mathematical model of the show goes like this. The contestant is shown three closed doors. Behind one is an expensive car, and behind the other two are goats.