2. gas mileage was compared for premium and regular gas for twenty toyota prius’s. each car was run on a tank of premium gas and on a tank of regular gas. before the study, a coin was tossed for each car. if the coin was heads, the car was first tested with premium gas; if the coin was tails, the car was first tested with regular gas. at the end of the study, average miles per gallon for the two types of gas was compared. what type of study is this?