We want to conduct a hypothesis test of the claim that the population mean score on a nationwide examination in anthropology is different from 536. So, we choose a random sample of exam scores. The sample has a mean of 518 and a standard deviation of 72. For each of the following sampling scenarios, choose an appropriate test statistic for our hypothesis test on the population mean. Then calculate that statistic. Round your answers to two decimal places. (a) The sample has size 15, and it is from a normally distributed population with a known standard deviation of 76. Oz = O It is unclear which test statistic to use. (b) The sample has size 12, and it is from a normally distributed population with an unknown standard deviation. Ot = %3D O It is unclear which test statistic to use.