The tensile strength of stainless steel produced by a plant has been stable for a long time with a mean of 72 kg/mm2 . a machine was recently adjusted and a sample of 10 items were taken to determine if the mean tensile strength has changed. the mean of this sample is 75.00 and the standard deviation of this sample is 2.56. a) at the 0.05 level of significance, is there evidence that the population mean of the tensile strength has changed from 72 kg/mm2 after the machine was adjusted. (15 points) b) find a 95% confidence interval for the mean of tensile strength after the machine was adjusted.