In the population, it is hypothesized that flags have a mean usable life of 100 days. Twenty-five flags are flown in the city of Tuscaloosa and are found to have a sample mean usable life of 200 days with a standard deviation of 216 days. Does the sample mean in Tuscaloosa differ from that of the population mean?
a. Conduct a two-tailed t test at the .01 level of significance.
b. Construct a 99% CI.