Key Metrics in Six Sigma

DPU

average defects per unit produced;

Total defects / total units produced

DPMO

defects per million opportunities; (total defects / (# of units*# opportunities))*1,000,000;

How many chances there are for a defect to occur in each unit

2 sigma

308k DPMO

1 sigma

690k DPMO

3 sigma

66,800 DPMO

4 sigma

6210 DPMO

6 sigma

3.4 DPMO

5 sigma

233 DPMO

total opportunities formula

units produced*defect opportunities

Rolled Throughput Yield (RTY)

Represent the chance of defect-free flow through all process steps; Y1%*Y2%*Y3%*...Yn%;

n% chance that a unit will successfully pass all 3 steps without defects

cycle time

Time to complete a single process step

lead time

the total duration from customer request to final delivery

takt time

the pace products must meet to meet demand; Available production time / customer demand value

cost of poor quality (COPQ)

Expenses caused by defects and mistakes

prevention costs

actions like training to avoid defects

appraisal costs

include inspections and testing activities

internal failure costs

arise from defects found before product delivery

external failure

when defective products reach customers, causing returns or repairs

pareto analysis

list all defects and costs, organize from highest to lowest costs, and use rankings to find defects that contribute to COPQ the most