NOS: The Notion of a Fair Test

What is a fair test? When we discuss science experiments with younger children, we refer to them as "fair tests". Often we pull out a set of identical balls that bounce very differently and ask the question, "How can we tell which ball bounces the highest?" Students will readily ask you to drop them and see. So when you drop one from a higher point that the other, they immediately scream, "thats not fair!" Then you drop one and throw the other down - again with the protests. Eventually you can lead the students to controlling all the "variables" that could affect the bounce in a ball and your method is designed. The discussion can even get to the point where students are designing apparatus for making sure the release is simultaneous and identical for both balls.

Once the test is fair, you need to ask, How will we know which ball bounce highest? The students will then come up with a variety of ways to measure the quality of the bounce.