I Six Sigma Define and Measure

Question 1

What is the Six Sigma System?

Answer 1

“The Six Sigma system is a comprehensive and flexible system for achieving, sustaining and maximizing business success.”

Achieve a near-perfect, 6σ, quality – the defect rate in the production of each component will not be more than 3.4 parts per million.

Question 2

Who invented the term “Six Sigma”

Answer 2

The term “Six Sigma” was coined by Bill Smith at Motorola. Motorola officially launched its Six Sigma program in 1987.

Question 3

What is the used of the term “Sigma”?

Answer 3

The term “sigma” is used to designate the distribution or spread about the mean (average) of any process or procedure.

Question 4

What is the sigma capability (z-value)?

Answer 4

For a process, the sigma capability (z-value) is a metric that indicates how well that process is performing.

The higher the sigma capability, the better the process. Sigma capability measures the capability of the process to produce defect-free outputs.

Question 5

When does a defect occur?

Answer 5

A defect occurs during any process step when the outcome of the process step is not the expected outcome.

Question 6

What are the themes of Six Sigma?

Answer 6

• Focus on the Customer
• Data and Fact-Driven Management
• Process Focus
• Proactive Management
• Boundaryless Collaboration
• Drive for Perfection (with tolerance for failure)

Question 7

What is the DMAIC Process Improvement Cycle?

Answer 7

• Define
• Measure
• Analyze
• Improve
• Control

Question 8

What is included in the DMAIC Define process?

Answer 8

• Customer expectations: Voice of the Customer Critical-to-Quality parameters
• Project goal
• Project team
• Milestones, budget
• Basic process flow

Question 9

What is included in the DMAIC Measure process?

Answer 9

• Process mapping
• Sampling plan design
• Measure CTQ parameters –establish process capability
• Measure influencing parameters

Question 10

What is included in the DMAIC Analyze process?

Answer 10

• Causal hypotheses
• Key influencing factors for Critical-to-Quality parameters
• Prioritization of improvement projects

Question 11

What is included in the DMAIC Improve process?

Answer 11

• Establish a hypothesis to be tested.
• Analyze the data for the new process to show that the implemented changes result in an improved process and quantify this improvement

Question 12

What is included in the DMAIC Control process?

Answer 12

• Statistical Process Control

* Control Charts

Question 13

What is a defect?

Answer 13

A defect occurs during any process step when the outcome of the process step is not the expected outcome.
The expected outcome means that the conditions of the outcome are specified in advance.

Random Defects: unwanted particles
Systematic Defects: process problem

Question 14

How are the levels of defects measured?

Answer 14

p= # of defective units produced at a process step / total number of produced units going into the process step(“fraction defective”)

Yield = # good units produced at a process step / # total units going into the process step

=1 –p

Question 15

How you measure the Process Yield?

Answer 15

Yield= # good units produced at a process step / # total units going into the process step = 1-p

If you have more than one process step (or part) to make your product where

n: number of process steps (or parts)

1 -p: yield at each process step (all steps or parts have same yield) then the overall good units coming out of the entire process is the

Process Yield* = (1 -p)n

(1) For 10000process steps, each with 1% fraction defective what is our final process yield? 1 -p = 1 –0.01 = 0.99 = 99% yield at each step.

Process Yield = (0.99)10000= (2.25×10)^-44= pretty much zero!

(2) For10000 process steps, each with 3.4×10-4 % fraction defective what is our final process yield? 1 -p = 1 –0.0000034=0.9999966 = 99.99966% yield at each step.

Process Yield = (0.9999966)^10000= 0.97 = 97% good parts!!

Question 16

What the ppm?

Answer 16

Parts per Million

ppm=# defective units / million units = p×1 million

p= # of defective units / total number of produced units = “fraction defective”

ppm= # defective units ×million units
= p×1 million

For a 99.379% yield at each step what is the ppm?
1 -p = 0.99379
p = 1 -0.99379 = 0.0621
ppm = 0.0621×1000000
= 6210

Question 17

What is a DPU?

Answer 17

Defects per Unit, the average number of defects per unit of product. Is a measure of the average number of defects per unit.

DPU= Total # of Defects / Total # of Units

Question 18

What is a DPMO?

Answer 18

Defects per Million Opportunities

Defects per Million Opportunities (DPMO) differentiates between products with many “Defect Opportunities” (drill) and those with few defect opportunities (pencils). If each unit has several opportunities per unit to be defective, then we can use the metric DPMO, Defects per Million Opportunities:

DPMO= DPU×1000000 / Total Opportunities for a Defect in One UnitTotal

Difference to ppm?
DPMO: Parts or processes can have more than one defectopportunity.
vs. ppm which is # defectiveunits / million units

Question 19

What is CTQ?

Answer 19

If we identify a key variable –a variable that is “Critical-To-Quality” for the product, then we can monitor this variable to help us monitor the defect rate. We will call this variable the “CTQ” variable.