Common Abbreviations Used in Six Sigma

Symbol/Acronym	Meaning
ANOVA	Analysis of variance
COPQ	Cost of poor quality
DFSS	Design for six sigma
DOE	Design of experiments
Dpm (DPM)	Defects per million
FMEA	Failure mode and effect analysis
LCL	Lower control limit
LSL	Lower specification limit
PSM	Program safety management
ROI	Return on investment
RPN	Risk priority number
SOP	Standard operating procedure
SPC	Statistical process control
UCL	Upper control limit
USL	Upper specification limit
MPIW	Mistake proofing improvement worksheet
e	Base of natural logarithm (2,718)
μ	Population mean
∑	Summation
σ	Population standard deviation
σ2	Population variance
n	Sample size
N	Population size
p	Probability or sample proportion
r2	Sample coefficient of determination
s	Sample standard deviation
s2	Sample variance
	Sample mean