Six Sigma Measurement
Yield and Defects LSL Target Value USL Probability of Defects Probability of Yield
The Normal Curve 2 3 4 5 6 68,26 % 95,46 % 99,73 % 99,9937 % 99, % 99, % 2 3 4 5 6 -6 -5 -4 -3 -2 +1 +2 +3 +4 +5 +6
Statistical Interpretation of Six Sigma Let “X” be the quality characteristic of interest and (Length/Thickness/Temperature/Pressure etc.) USL = Upper Specification Limit LSL = Lower Specification Limit T = Target Value Process Average Process Standard Deviation X = Estimate of s = Estimate of
Calculation of Sigma level - When Process is Centered SIGMA LEVEL (Z) = USL - T s SIGMA LEVEL (Z) = T - LSL s OR ULMean = T
Calculation of Sigma level SIGMA LEVEL (Z) = X - LSL s When Process is Centered Closer To LSL ULTMean
Calculation of Sigma level SIGMA LEVEL (Z) = USL - X s When Process is Centered Closer To USL ULTMean
Calculation of Sigma level SIGMA LEVEL (Z) = USL - X s There is only Upper Specification Limit (USL) UMean
Calculation of Sigma level SIGMA LEVEL (Z) = X - LSL s There is only Lower Specification Limit (LSL) LMean
The Normal Curve wit Different Sigma Levels 1298 = LSL USL = 1322 USL = 1310 S = 2 (SIX SIGMA Quality Level) S = 3 (FOUR SIGMA Quality Level) S = 4 (THREE SIGMA Quality Level)
SIGMA LEVELDPMO 1 6,97, ,08, , , SIGMA ( ) QUALITY LEVELS (DPMO)
Converting Yield to Sigma Level Without Shift
DPMODPMO MEANS DEFECTS PER MILLION OPPORTUNITIES IS TRANSLATED INTO A SIGMA NUMBER Opportunities for Defect
Formula = Number of Defects # of Units x # of opportunities Formula = 319 defects on joints 1150 Units x 15 opportunities/joist Example 319 Defects, 1150 Items, 15 defect opportunity = DPO = x 10 6 =18,000 DPMO Defects/Opportunity & Defect/Million Opportunity