A computer system administrator in the statistics department at Penn State observes that computers running a particular operating system seems to freeze-up more often as the installation of the operating system ages. He measures the freeze-up time (in minutes) for 7 computers one month after the installation, and for 9 computers eight months after the installation. Results are shown in the below table:

\fOne moth from installation. Eight months from installation. 207.4 233.1 215.9 235.1 84.3 53.2 127.3 201.3 225.6 244.4 245.3 174.2 246.2 149.4 156.4 103.3 n = 7, x = 229.54, $2 = 200.76 n = 9, x = 114, s' = 3570.9