The following was information is given:
Average: `barx = 85.02`
Standard Deviation: `SD = 0.188441`
Upper Specification Limit:`USL = 85 + 0.5 = 85.5`
Lower Specification Limit: `LSL = 85 - 0.5 = 84.5 `
a. What is the Cp value
Cp is simple and straightforward indicator of process capability.
Cp is mathematically calculated as follows:
`C_p = (USL - LSL)/(6*SD)`
`C_p = (85.5 -84.5)/(6*0.188441) = 0.88445`
b.What is the Cpk value?
Cpk is an indicator that measures how close to the target as well as how centered you are around the average.
Mathematically Cpk is calculated as follows:
`C_(pk) = min ((USL-barx)/(3*SD),(barx-LSL)/(3*SD))`
`C_(pk) = min ((85.5-85.02)/(3*0.188411),(85.02-84.5)/(3*0.188411))`
`C_(pk) = min (0.849207318, 0.9199745945)`
Using an online calculator we can find the answer to the above calculation (reference below):
`C_(pk) = 0.849`
c. Three options for improving process capability:
- Evaluate the Process Flowchart
When looking at the process flowchart, look for areas where work has been duplicated. If there are areas of duplication, speak to the stakeholders to have the duplication removed as these steps are not necessary in providing a quality product or service to the customer.
- Evaluate the Control Charts
Look at the control and look for outliers or huge variability. If this is caused by a common cause, then the variation is existent in every process (not process is 100% perfect), but if it a special cause variation, then one should look into it and find ways to improve it. Special cause variation occurs at unusual circumstances.
Find New Improvements
If the control charts seems to be causing huge variations, new control charts needs to be developed to improve the process capability. Any improvements or changes made that require training of workers should be done by first training the employees.
SUMMARY:
a. Cp = 0.884
b. Cpk = 0.849
c. Evaluate the process flowchart, evaluate the control charts and find new improvements.
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