A tire company wants to determine if tires made with a new type of tread will last longer than tires made with the original type of tread. The company decides to put tires with the new tread on 10 different vehicles and tires with the original tread on 10 different vehicles. "New” is written on one slip of paper and "Original” is written on another slip of paper. The two slips are placed in a bag and thoroughly mixed. A vehicle is selected and a slip is drawn. The corresponding tread of tires is assigned to the vehicle. The slip is put back into the bag and mixed. The next vehicle is selected and a slip is drawn. The corresponding tread is assigned to the vehicle. This procedure continues until all 20 vehicles have been assigned tires of the new or original types of tread.