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Is 99% Good Enough ?
Unsafe drinking water almost 15 minutes each day
2 short or long landings at most major airports daily
No electricity for almost 7 hours each month
Sample Data
3.2 g 3.0 g
3.1 g3.0 g
3.1 g 3.2 g
3.2 g3.2 g
3.3 g 3.2 g
3.2 g3.0 g
2.9 g 3.4 g
3.2 g3.0 g
3.3 g 3.2 g
3.2 g3.3 g
3.1 g 3.1 g
3.2 g3.2 g
3.2 g 3.1 g
3.2 g3.3 g
3.2 g 3.1 g
2.9 g3.2 g
3.2 g 3.2 g
3.0 g3.2 g
Weight of stick gums
Histogram
Weight of stick gums
Normal Distribution
Weight of stick gums
Specification Limits
Weight of stick gums
Definitions and Examples• Critical to Quality, an attribute
important to the customerCTQ
• Any measurable event that provides a chance of not meeting specification limits of a CTQ
Opportunity
• Anything that results in customer dissatisfaction or in a non-conformance
Defect
• Defects per million opportunitiesDPMO
• The probability of defect, a measure of process capability, measured in units of standard deviations
Sigma Capability
In this example gum weight is a critical attribute
Every stick gum produced on the shop floor is an opportunity
Our pack weight indicates 3.0 g. We consider getting below 3.0 g as a defect since the customer will feel short changed. We also consider going beyond 3.4g as a defect. While customer will be happy getting more, we will lose money for our material cost.
These will be the number of defective stick gums if 1 million is produced.
Computation of sigma capability is done in the Six Sigma Greenbelt training
Defects
Weight of stick gums
Mean and Spread
Weight of stick gums
mean
standard deviation
Process Capability
Poor
Good
Higher probability of defects
Lower probability of defects
Sigma Level vs DPMO
Sigma Level PPM
2 308,537
3 66,807
4 6,210
5 233
6 3.4
Process Capability DPMO
Sigma Level vs DPMO
Sigma Level PPM
2 308,537
3 66,807
4 6,210
5 233
6 3.4
Process Capability DPMO
Average Company
In Real World
At 99% (3.8 Sigma) At 99.99966% (6 Sigma)
Unsafe drinking water almost 15 minutes each day
One minute of unsafe drinking water every seven months.
In Real World
At 99% (3.8 Sigma) At 99.99966% (6 Sigma)
2 short or long landings at most major airports daily
One short or long landing at most major airports every 5 years.
In Real World
At 99% (3.8 Sigma) At 99.99966% (6 Sigma)
No electricity for almost 7 hours every month
One hour without electricity every 34 years
The Six Sigma Difference
CenterProcess
ReduceSpread
Defects
The Statistical ObjectiveProcess Off Target Excessive Variation
Poor ProcessCapability
Good ProcessCapability
Reduce Variation and Center Process
USLLSL USLLSL
USLLSL
LSL Lower specification limit
USL Upper specification limit
Y = f (X)
DMAIC Methodology
Y = Desired characteristic
X = Internal Process Characteristic
• Customer expectation of the processDefine• Frequency of the defectsMeasure• Why the defects occur?Analyze• How can we fix it?Improve• How can we sustain the solution?Control
Structured, Data-driven Approach
Six Sigma as a Strategy
Savings of $ 940 M in 3 years
Improved Operating Margin by 4% in 5 years
Saves $100,000 - $200,00 per project
What is Six Sigma ?A process description – a measurement of a process that
has only 3.4 defects per million opportunities
A methodology – a structured and data driven approach to deliver improved customer quality
A business strategy – satisfying the customer through robust management of the end to end process
