An article in Journal of the Operational Research Society [A Quality Control Approach for Monitoring Inventory Stock

An article in Journal of the Operational Research Society [€œA Quality Control Approach for Monitoring Inventory Stock Levels,€ (1993, pp. 1115€“1127)] reported on a control chart to monitor the accuracy of an inventory management system. Inventory accuracy at time t, AC(t), is defined as the difference between the recorded and actual inventory (in absolute value) divided by the recorded inventory. Consequently, AC(t) ranges between 0 and 1 with lower values better. Extracted data are shown in the following table.

(a) Calculate individuals and moving-range charts for these data.

(b) Comment on the control of the process. If necessary, assume that assignable causes can be found, eliminate suspect points, and revise the control limits.

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3 4 6. 8. 9. 10 11 AC(t) 0.050 0.095 0.055 0.200 0.105 0.190 0.030 18 0.075 0.090 0.115 20 0.103 0.121 15 0.098 17 0.298 19 14 12 0.089 13 0.180 16 0.173 21 0.147 22 0.079 0.083 0.122 AC(t) 0.115 =