A producer of various kinds of batteries has been producing "D" size batteries with a life expectancy of 87 hours. Due to an improved production process, management believes that there has been an increase in the life expectancy of their "D" size batteries. A sample of 36 batteries showed an average life of 88.5 hours. Assume from past information that it is known that the standard deviation of the population is 9 hours.
a. Give the null and the alternative hypotheses.
b. Compute the test statistic.
c. At 99% confidence using the critical value approach, test management's belief.
d. What is the p-value associated with the sample results? What is your conclusion based on the p-value?