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:

Find a 95% confidence interval for the mean difference in time to freeze-up between the first month and the seventh?

Transcribed Image Text:

One month after insa 207.4 233.1 215.9 235.1 225.6 244.4 245.3 Seven months after instal: 84.3 53.2 127.3 201.3 174.2 246.2 149.4 156.4 103.3