A battery manufacturer advertises their batteries to have a capacity of 4000 mAh. To deliver their promise, they make sure that the capacity of their batteries are between 3950 mAh and 4050 mAh. Additionally, to find out if the manufacturing process consistently produces the desired quality every hour, they recorded the capacity of 7 batteries (subgroup size = 7) hourly during a 10-hour shift for a sample size of 70 batteries.