FarmaSuitica, Inc, a mail-order prescription drug vendor, measured the number of defects per standard 200 line order being picked in their distribution center. Construct c-chart for data in the table in the worksheet Prob 07-08 in the ch07 data.xlsx file and interpret the results.
| Number of Defects | |||
| Sample | per order (200 product order) | ||
| 1 | 1 | ||
| 2 | 2 | ||
| 3 | 1 | ||
| 4 | 1 | ||
| 5 | 2 | ||
| 6 | 4 | ||
| 7 | 1 | ||
| 8 | 3 | ||
| 9 | 1 | ||
| 10 | 1 | ||
| 11 | 1 | ||
| 12 | 2 | ||
| 13 | 3 | ||
| 14 | 0 | ||
| 15 | 2 | ||
| 16 | 3 | ||
| 17 | 2 | ||
| 18 | 5 | ||
| 19 | 1 | ||
| 20 | 3 | ||
| 21 | 0 | ||
| 22 | 0 | ||
| 23 | 1 | ||
| 24 | 2 | ||
| 25 | 1 | ||
| 26 | 1 | ||
| 27 | 2 | ||
| 28 | 1 | ||
| 29 | 4 | ||
| 30 | 1 | ||
Total number of defects in 30 samples = 52
Therefore , average number of defects per sample = Cbar = 52/30 = 1.733
Therefore ,
Upper Control Limit ( UCL) = Cbar + 3 Square root ( Cbar ) = 1.733 + 3xSquare root ( 1.733) = 1.733 +3 x 1.316= 1.733+3.948=5.681
Lower control Limit ( LCL ) = Maximum ( 0. Cbar – 3 x Square root ( Cbar) ) = Maximum ( 0 , 1,733 – 9.948) = 0
Thus it can be said that as long as number of defects in all the samples are within range0 – 5.681 ,it can be said that the process is in control.
The data furnished in the problem caseregarding number of defects per sample have minimum value of 0 and maximum value of 5 and thus fall within control limits 0 – 5.681 .
Therefore, it can be concluded that the process is in control
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