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Capability Analysis An Introduction to Statistical Process Control

Capability Analysis An Introduction to Statistical Process Control. Course Content. Course Objectives What is Variation? Seeing Variation Measuring Variation Normal Distribution Cp and Cpk Calculations Pp and Ppk Calculations Examples Review Additional Resources. Course Objectives.

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Capability Analysis An Introduction to Statistical Process Control

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  1. Capability Analysis • An Introduction to Statistical Process Control

  2. Course Content • Course Objectives • What is Variation? • Seeing Variation • Measuring Variation • Normal Distribution • Cp and Cpk Calculations • Pp and Ppk Calculations • Examples • Review • Additional Resources

  3. Course Objectives • Upon completion of this course, participants should be able to: • Understand why measuring variation is important • Calculate mean, standard deviation, Cp and Cpk • Estimate the percent of data beyond the specifications • Interpret the results of a capability analysis • Understand how to improve the capability of a product or process

  4. Skewed Distributions mean = median mean median median mean Average class shoe size – No skew Time to drive to work – Skewed right Hours of sleep per week – Skewed left

  5. Standard Deviation • Standard Deviation (σ) = the average difference of each value from the mean √ Σ(x - )2 Std dev = n -1 It is a measure of how spread apart each individual data point is from the mean

  6. What is Cp? • Cp is a measure of how well the variation in the data can fit within the tolerance limits If the variation (6σ) is less than the tolerance limits, you have acceptable variation If the variation (6σ) is greater than the tolerance limits, you have unacceptable variation LL UL LL UL 6σ 6σ

  7. Examples USL Cpk = 0.33 15.87% Predicted failure rate -3 -2 -1 0 +1 +2 +3

  8. Difference between Cp/Cpk and Pp/Ppk • Cp/Cpk • Uses within estimate of standard deviation • Estimates potential capability (if outliers removed) • Estimates short term variability • Pp/Ppk • Uses overall standard deviation formula (assumed for this course) • Estimates actual capability (includes outliers) • Estimates long term variability Unsure? Use Pp and Ppk calculations to be safe

  9. Additional Resources Business Performance Improvementhttp://www.biz-pi.com

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