Miguel found 20 teenagers with the same sized scrapes on their knees. He made sure they were the same size by measuring the length and width. He wanted to know if taking vitamin C tablets could help speed up the healing time of their scrapes. He gave 10 of the people 1 vitamin C every day for 1 week. The other 10 people did not take a pill during the week. After a week’s time, he looked at everyone’s scrapes to see how they healed.