Computer crashes: A computer system administrator notices that computers running a particular operating system seem to crash more often as the installation of the operating system ages. She measures the time (in minutes) before crash for six computers one month after installation, and for nine computers seven months after installation. The results are as follows: One month after installation 217 209 230 230 247 243 Seven months after installation 85 59 129 201 176 240 149 154 105 Send data to Excel Part: 0/3 Part 1 of 3 (a) Explain why it is necessary to check whether the populations are approximately normal before constructing a confidence interval. Since the sample size is small approximately normal. it is necessary to check that the populations are Part: 1/3 Part 2 of 3 (b) Following are dotplots of these data. Is it reasonable to assume that the populations are approximately normal? < 200 210 50 100 It is Part: 2/3 Part 3 of 3 220 230 One month after installation 150 # 240 250 200 250 Seven months after installation reasonable to assume that the populations are approximately normal. (c) Construct a 90% confidence interval for the mean difference in time to crash between the first month after installation and the seventh. Let denote the mean time to crash one month after installation. Use the TI-84 calculator and round the answers to one decimal place. A 90% confidence interval for the mean difference in time to crash between the first month after installation and the seventh is