Cheryl practices hitting a softball in an indoor stadium by using both an aluminum bat and a composite bat made of carbon fiber and graphite. She records the distance traveled by the ball for each hit. Let x¯1x¯1 represent the average distance traveled by balls hit with the aluminum bat, and let x¯2x¯2 represent the average distance traveled by balls hit with the composite bat. Assume Cheryl's batting practice hits are independent.
Which of the following conditions are sufficient to model the sampling distribution of x¯1−x¯2x¯1−x¯2 with a normal distribution?
There are at least 30 recorded distances traveled for each type of bat.
The distribution of distance traveled by the ball is approximately normal for each bat.
The total number of distances traveled is at least 60 for the two bats combined
