# 5 tri state bank is investigating the processing time

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5.* Tri-State Bank is investigating the processing time for loan applications. Samples were taken for 25 random days from 4 branches. These data can be found in the worksheet C16P5 in the OM6 4
OM6 C16 IM Data Workbook . Construct control charts using the Excel template xBar&R-chart . Verify the Excel calculations of the control limits by hand using the formulas in the chapter. Does the process appear to be in statistical control? Why or why not? Portions of the spreadsheet template are shown below: LCLx-bar 7.19928 Center 18.63 UCLx-bar 30.0607 2 LCLrange 0 Center 15.68 UCLrange 35.7817 6 5
OM6 C16 IM
6. Twenty-five samples, each consisting of 200 loan applications at a bank, resulted in a total of 40 applications that had some type of error. Compute the control limits for a p -chart.
7.* Eightly insurance claim forms are inspected daily for 25 working days, and the number of forms with errors are recorded in the worksheet C16P7 in the OM6 Data Workbook Construct a p -chart using the Excel template p-Chart . Verify the Excel calculations of the control limits by hand using the formulas in the chapter. If any special causes are identified, remove them from the data and construct a revised control chart. .
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OM6 C16 IM On average, this insurance claim process generates 2.4% errors. Portions of the Excel template are shown below (differences in formula calculations due to rounding): 1 7 4 10 13 16 19 22 25 28 31 34 37 40 43 46 49 0.0000 0.0200 0.0400 0.0600 0.0800 0.1000 0.1200 0.1400 Attribute (p) Chart Fraction noncon- forming Lower control limit Center line Sample number Fraction nonconforming 7
OM6 C16 IM Based on the control limits, we would expect a maximum of about 7.5% errors. Samples 13 and 19 are outside of the control limits and are most likely due to a special cause. If these are removed (by simply deleting the cells in column B of the template), the revised control chart is shown next and is now in control. It is assumed that an improvement team was set up to investigate samples 13 and 19 and a root cause was found and fixed. The team may have used all of the tools and concepts of Chapters 15 and 16. 8
OM6 C16 IM In the template, be sure that students realize that when deleting 2 points, the number of samples is now only 23! 9
OM6 C16 IM 1 7 4 10 13 16 19 22 25 28 31 34 37 40 43 46 49 0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600 0.0700 Attribute (p) Chart Fraction noncon- forming Lower control limit Center line Sample number Fraction nonconforming