An electrical engineer wishes to compare the mean lifetimes of two types of transistors in an application involving high-temperature performance. a sample of 60 transistors of type a were tested and were found to have a mean lifetime of 1827 hours and a standard deviation of 164 hours. a sample of 180 transistors of type b were tested and were found to have a mean lifetime of 1658 hours and a standard deviation of 219 hours. let μx represent the population mean for transistors of type a and μy represent the population mean for transistors of type b. find a 95% confidence interval for the difference μx−μy . round the answers to three decimal places.