Alejandro owns a restaurant where he sells pizza by the slice. He wonders if customers prefer their pepperoni on top of the cheese or under the cheese. Every day for a week, he prepares both types of pizza. Every time a customer orders a slice of pepperoni pizza, he flips a coin to determine whether he'll give the customer a slice with pepperoni on top or under the cheese. He then asked each customer to rate their pizza. At the end of the week, he found that customers who received pepperoni on top rated their pizza significantly better on average than customers who received pepperoni under the cheese. What conclusion can they draw from this study