Six Sigma Tutorial -> Six Sigma Capability Improvement

Six Sigma Capability Improvement

Defect Based Six Sigma Metrics - Example

If there are 9 defects among 150 invoices, and there are 8 opportunities for errors for every invoice, what is the dpmo?

dpu = no. of defects / total no. of product units = 9/150 = .06 dpu

dpo = no. of defects / (no. of units X no. of defect oppurtunities per unit)

      = 9/(150 X 8) = .0075 dpo

dmpo = dpo x 1,000,000 = .0075 X 1,000,000 = 7,500 dpmo

What are the equivalent Sigma and C_P values? See Sigma Table.

Converting Yield to sigma & C_p Metrics - Example

Given: a proportion defective of 1%
 

• Yield = 1 - p = .990
• Z Table value for .990 = 2.32σ
• Estimate process capability by adding 1.5 σ to reflect the 'real-world' shift in the process mean
  
           2.32σ + 1.5σ = 3.82σ
   
• This σ value can be converted to an equivalent C_P by dividing it by 3σ :
  
           C_P = 3.82σ/3σ = 1.27
  
  Note: C_pk cannot be estimated by this method
   

Six Sigma Capability Improvement

Sigma Table

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