Q: What does the Pareto 80/20 rule mean?

The Pareto principle states that 80% of all defects originate from 20% of all defect causes. A Pareto chart is a bar chart of defect types ordered by frequency, overlaid with a cumulative percentage curve. By focusing improvement efforts on the vital few causes that exceed 80% cumulative percentage, maximum effect can be achieved with minimum effort.

Q: What are the 6M categories of the fishbone diagram?

Kaoru Ishikawa's (cause-and-effect diagram) 6M categories: Man, Machine (equipment), Method, Material, Measurement, and Mother Nature (environment). Brainstorming is conducted by identifying potential causes in each category. The 6M is standard in manufacturing, but variations such as 4P or 5S are used in service industries.

Question 1

What is the relationship between DPMO and sigma level?

Accepted Answer

DPMO (Defects Per Million Opportunities) = (Defects / (Units × Opportunities)) × 1,000,000. DPMO to sigma level (long-term with 1.5σ shift): 2σ=308,537, 3σ=66,807, 4σ=6,210, 5σ=233, 6σ=3.4. The Six Sigma goal is 3.4 long-term DPMO or less.

Question 2

What are the acceptance criteria for Gauge R&R (MSA)?

Accepted Answer

%R&R (Gage R&R) = σ_gauge/σ_total × 100%. Criteria: %R&R < 10% is excellent; 10–30% is acceptable (depending on application and cost); >30% requires improvement and the measurement system is inadequate. The P/T ratio (precision/tolerance) = 5.15×σ_gauge/(USL−LSL) is acceptable at <0.1.

Question 3

What does the Pareto 80/20 rule mean?

Accepted Answer

The Pareto principle states that 80% of all defects originate from 20% of all defect causes. A Pareto chart is a bar chart of defect types ordered by frequency, overlaid with a cumulative percentage curve. By focusing improvement efforts on the vital few causes that exceed 80% cumulative percentage, maximum effect can be achieved with minimum effort.

Question 4

What are the 6M categories of the fishbone diagram?

Accepted Answer

Kaoru Ishikawa's (cause-and-effect diagram) 6M categories: Man, Machine (equipment), Method, Material, Measurement, and Mother Nature (environment). Brainstorming is conducted by identifying potential causes in each category. The 6M is standard in manufacturing, but variations such as 4P or 5S are used in service industries.

Process	Characteristic	Specification	Control Method	Frequency

Six Sigma DMAIC Toolkit

DPMO & Sigma Level Conversion Table

Sigma Level	DPMO (Long-term)	Defect Rate %
2σ	308,537	30.85%
3σ	66,807	6.68%
4σ	6,210	0.62%
5σ	233	0.023%
6σ	3.4	0.00034%