DPO, DPMO, PPM, DPU Definitions – Six Sigma Defect Metrics
What Is DPO? What Is DPMO?
A unit of product can be defective if it contains one or more defects. A unit of product can have more than one opportunity to have a defect.
- Determine all the possible opportunities for problems
- Pare the list down by excluding rare events, grouping similar defect types, and avoiding the trivial
- Define opportunities consistently between different locations
Proportion Defective (p):
p = Number Of Defective Units / Total Number of Product Units
Yield ( Y1st-pass or Yfinal or RTY)
Y = 1 – p The Yield proportion can converted to a sigma value using the Z tables
Defects Per Unit – DPU, or u in SPC
DPU = Number Of Defects / Total Number Of Product Units The probability of getting ‘r’ defects in a sample having a given dpu rate can be predicted with the Poisson Distribution.
Defects Per Opportunity – DPO
DPO = no. of defects / (no. of units X no. of defect opportunities per unit)
Defects Per Million Opportunities (DPMO, or PPM)
DPMO = dpo x 1,000,000 Defects Per Million Opportunities or DPMO can be then converted to sigma & equivalent Cp values in the next page. The DPMO, DPM, Sample Size, CI Calculator will help you calculate the metrics.
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 CP values? See Sigma Table.
Converting Yield to sigma & Cp 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 CP by dividing it by 3σ : CP = 3.82σ/3σ = 1.27 Note: Cpk cannot be estimated by this method
Six Sigma Capability Improvement
|Yield||dpmo||Sigma (σ)||Cp Equiv.||COPQ (Cost of Poor Quality)|
Our free DPMO, DPM, Sample Size, CI Calculator will help you calculate the metrics.