We want to conduct a hypothesis test of the claim that the population mean time it takes drivers to react following the application of brakes by the driver in front of them is less than 2.2 seconds....

Extracted text: We want to conduct a hypothesis test of the claim that the population mean time it takes drivers to react following the application of brakes by the driver in front of them is less than 2.2 seconds. So, we choose a random sample of reaction time measurements. The sample has a mean of 2.1 seconds and a standard deviation of 0.4 seconds. 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 l18, and it is from a normally distributed population with an unknown standard deviation. t = O It is unclear which test statistic to use. (b) The sample has size 15, and it is from a normally distributed population with a known standard deviation of 0.45. O z O It is unclear which test statistic to use.