Josiah uses a pencil called Brand A. He has pencil smears on his paper every time he completes an assignment and he hates this! Caleb is using a pencil called Brand B. Josiah notices Caleb never has smears on his paper. Josiah wonders if it's the brand of pencil that's keeping Caleb from getting smears on his paper. He decides to borrow Caleb's pencil and test the brand against his to find out. Hypothesis:

What is another variable that Josiah could test in this situation as a 2nd experiment?