Question 3 (2 marks) A random sample of 15 values was selected from a population, and the sample standard deviation was computed to be 137. Based on this sample result, compute a 90% confidence interval estimate for the true population standard deviation. Question 4 (3 marks) A purchasing agent needs to find the most durable aluminum at the best possible price. To compare durability, pressure is put on the aluminum until it cracks. The vendor whose aluminum requires the greatest average pressure will be judged to have the most durable product. For this test, 13 pieces from each of two vendors are selected at random. The results in pounds per square inch (psi) are shown in the table. The agent is concerned about whether the assumption of equal population variances was satisfied. Conduct the appropriate hypothesis test make sure to clearly show all the steps). Vendor 1 n = 13 x = 2,368 psi $ = 350 Vendor 2 n = 13 x2 = 2,445 psi $2 = 300