In: Statistics and Probability
A computer system administrator notices that computers running a particular operating system seem to freeze up more often as the installation of the operating system ages. She measures the time (in minutes) before freeze-up for seven computers one month after installation, and for nine computers seven months after installation. The results are as follows: One month after install: 207.4 233.1 215.9 235.1 225.6 244.4 245.3 Seven months after install: 84.3 53.2 127.3 201.3 174.2 246.2 149.4 156.4 102.3 Let μX represent the population mean for the first month and let μY represent the population mean for the seventh month. Find a 95% confidence interval for the difference μX−μY . Round down the degrees of freedom to the nearest integer and round the answers to three decimal places.