Question

.A student sets up a controlled experiment to test whether aluminum bats hit baseballs further than wooden bats. After measuring the distance travelled by hundreds of struck baseballs, by both high school and professional players, he concludes that wooden bats hit baseballs further because professional players use wooden bats and hit the ball much further than high school players who use aluminum bats.
Where is the flaw in his approach?

Answer 1

His flaw is that he used professional players and high school players this makes the experiment uncontrolled because the players are at two levels of strength.