(08.05 MC) Hunter wants to prove to his parents that playing…

(08.05 MC) Hunter wаnts tо prоve tо his pаrents thаt playing computer games while he studies for tests will help him get better grades. He decides to ask 30 of his friends if they play computer games while they study for their tests and what their grades are. He finds that his friends who have high grades also play computer games while they do their homework. He tells his parents that he has proven that playing games while studying for tests will cause his grades to improve. What mistake has Hunter made?