Hotpot stoves use a standard oven insulation. To test its effectiveness they take random samples from the production line and heat the ovens selected to 400"C, noting the time taken to cool to 350"C after switching off. For a sample of 8 ovens the times in minutes are: 15.7, 14.8, 14.2, 16.1, 15.3, 13.9, 17.2, 14.9 They decide to explore a cheaper insulation, and using this on a sample of 9 the times taken for the same temperature drop are: 13.7, 14.1, 14.7, 15.4, 15.6, 14.4, 12.9, 15.1, 14.0 Are the firm justified in asserting there is no real evidence of a different rate of heat loss? Obtain a 95 per cent confidence limit for the difference in median heat loss (a) with and (b) without a normality assumption. Comment critically on any differences between your conclusions