The Value of Control Groups in Causal Inference (and Breakfast Cereal)

A few years ago, I taught the following lesson in my daughter's kindergarden class and my graduate methods class in the same week. It worked pretty well in both. Anyone who has a kid in kindergarten, some good graduate students, or both, might want to try this. It was especially fun for the instructor.

To start, I hold up some nails and ask "does everyone likes to eat nails?" The kindergarten kids scream, "Nooooooo." The graduate students say "No," trying to look cool. I say I'm going to convince them otherwise.