Question 2 A technician in a quick oil change shop had the following service times (in minutes) for 12 randomly selected cars: Sample 1 2 3 4 4.5 4.6 4.5 4.7 4.3 4.5 4.6 4.5 4.2 4.4 4.4 4.8 a) Please choose the suitable control charts to test whether or not the process is in control. b) The specification for service time is between 4.1 minutes and 5.1 minutes, is the specification being met? Using the formulation sigma=(sqrtn)/(3)A_(2) bar(R) ( n is sample size and A_(2) refers to tables below) to estimate the standard deviation from average range. Sample size n 2 3 4 5 6 7 8 9 10 11 12 13. Mean Factor A2 1.880 1.020 0.729 0.577 0.483 0.419 0.373 0.337 0.308 0.285 0.266 0.249. upper limit d4 3.267 2.574 2.282 2.114 2.004 1.924 1.864 1.816 1.777 1.774 1.717 1.693 lower limit D3 0 0 0 0 0 0.076 0.136 0.184 0.223 0.256 0.283 0.307