Refer to Exercise 23. There the Boulder Fire Department conducted a study of average emergency response times for its two stations. Assume now that the two population standard deviations are unknown and the sample results were as follows: For the sample of emergency responses by the North Boulder Station, average response time was 16.2 minutes, with a sample standard deviation of 5.5 minutes. For the sample of emergency responses by the South Boulder Station, average response time was 14.3 minutes, with a sample standard deviation of 4.6 minutes. Set up the appropriate hypothesis test to test a “no difference in population means” null hypothesis at the 5% significance level, assuming sample sizes were
a. 12 emergency responses by the North Boulder Station and 12 emergency responses by the South Boulder station. Assume the population distributions are normal and have equal standard deviations.
b. 120 emergency responses by the North Boulder Station and 120 emergency responses by the South Boulder station.