A national pizza chain guarantees delivery of pizza orders within 20 minutes from the time of accepting an order; otherwise, the customer gets the pizza free of charge. Assume that actual delivery times in minutes for a random sample of seven customer orders were: 18, 17, 19, 20, 15, 25, and 30. Given this information,

1. How would you define variation in the pizza delivery process?

2. In the random sample of seven customers, how many customers got a free pizza?

3. What is the accuracy rate of this current delivery process?

4. If this pizza chain wants to be called a Six Sigma operation, what percentage of deliveries should it complete within 20 minutes from the time of accepting an order?