Students shouldn't freak out when things don't go exactly according to plan. There are ways to test whether results fit nicely into a statistical model or not. In statistics, the options for numerical tests are as numerous and appealing as germs on a hotel room comforter. By the way, good luck sleeping on your next vacation.
Students should be familiar with Goodness of Fit tests (which aren't the same tests used in JC Penney changing rooms). Students should also know that these tests help measure whether or not a statistical model fits certain observations.