A company is investigating two potential vendors on the timeliness of their deliveries. A random sample of size 10 from the first vendor produced an average delay time of 4.5 days with a standard deviation of2.3 days. A random sample of size 12 from the second vendor yielded an average delay time of 3.4 days with a standard deviation of 6.2 days.
(a) Find a 90% confidence interval for the ratio of the variances of the delay times for the two vendors. (b) What assumptions are needed to solve part (a)?
(c) Can we conclude that the first vendor has a smaller variability regarding delay times than that of the second? Use a significance level of 0.05.
(d) Which vendor would you select and why?