7.The mean running time of a certain variety of nickel-cadmium rechargeable flashlight battery is known to be normally distributed with a mean of 8.5. A change in production method for this battery has been proposed, and a simple random sample of 64 batteries produced by the new method has mean running time of 8.72 hours. Assume the population is normally distributed with a standard deviation of 0.55 hour as known and remains unchanged, test a claim that the new production method improving the battery mean running time using 0.05 significance level.

8.A company that makes cola drinks states that the mean caffeine content per 12-ounce bottle of cola 40 milligrams. You want to test this claim. During your tests, you find that a random sample of thirty 12-ounce bottles of cola has a mean caffeine content of 39.2 milligrams. Assume the population is normally distributed with a standard deviation of 7.5 milligrams. At =0.01, can you reject the company's claim?