LO2 13. The time needed for performing a machining operation is to be investigated. Historically, the process has had a standard deviation equal to 0.146 minute. The means (in minutes) of 39 samples of n = 6 are: Sample Mean Mean Sample Mean Sample 14......... 3.86 3.81 27......... 2 2........ 3.90 3.83 28.... 15......... 16..... 3.81 3.86 3.98 3 3.83 3.86 29. 3. 4. 3.81 17......... 3.82 30......... 5....... 3.84 3.86 31......... 6......... 3.83 18. 19. 20......... 3.84 32. 3.96 3.88 3.76 3.83 3.77 3.86 7......... 3.87 3.87 33.. 3.88 21...... 3.84 34..... 9...... 3.84 22...... 3.82 35......... 36.... 10.. 3.80 23 3.89 3.80 11. 3.88 24...... 3.86 37......... 3.84 3.86 25......... 3.88 38. 3.79 12..... 13.... 3.88 26.... 3.90 39... 3.85 Construct an X-chart for this process with Two Sigma lim- its. Is the process in control