Tread-on-us has designed a new tire, and they dont know what the average amount of tread in going to be. They do know that tread Life is normally distributed with a standard deviation of 216.4 miles (a) If the company Sampled 800 tires and records their tread life, what is the probability that sampe mean is between the true mean of 600 miles over the true man?
(b) How Large a sample must be taken & to be 95 percent sure the sample mean will be Within 100 miles of the truemean?