Olivia and Caitlyn want to know whether the wind affects how far a football will travel. They have one student go outside to the football field when it is not windy and throw the football 30 times. They measure how far the ball goes using a meter stick. On a windy day, they have the same student go to the football field and throw the football 30 times. Again, they measure how far the ball goes using the same meter stick. What is the Independent Variable?