Suppose That a Tire Manufacturer Believes That the Lifetimes of Its

Short Answer

Suppose that a tire manufacturer believes that the lifetimes of its tires follow a normal distribution with mean 48,000 miles and standard deviation 5,000 miles.
-If the manufacturer wants to issue a guarantee so that $99 \%$ of its tires last for longer than the guaranteed lifetime, what $z$ -score should it use to determine that guaranteed lifetime?