six sigma accidental split

Question 1

Q1. What type of probability distribution do most manufacturing processes follow?

Answer 1

A1. Manufacturing processes are mostly Gaussian (normal) due to many independent sources of variation.

Question 2

Q3. What are quantiles?

Answer 2

A3. Quantiles are cut-points that divide the total probability area into equal parts.

Question 3

Q2. What is the difference between a PDF and a CDF (theory only)?

Answer 3

PDF (Probability Density Function): describes likelihood of values

CDF (Cumulative Distribution Function): cumulative probability up to a given value

Question 4

Q4. Name the common quantiles used in statistics.

Answer 4

2 parts → median

4 parts → quartiles

10 parts → deciles

100 parts → percentiles

Question 5

Q5. What is process capability?

Answer 5

A5. The accuracy with which a process can produce parts, which must be less than the specified tolerance to be capable.

Question 6

Q6. Why do all manufacturing processes exhibit variation?

Answer 6

A6. Due to inherent statistical variation from factors such as:

Material properties

Tool hardness and wear

Thermal effects

Vibrations

Machine behaviour

Question 7

Q7. What does the Process Capability Index (PCI) represent?

Answer 7

A7. It shows how well a process fits within specification limits, i.e. how many times 6σ fits inside the tolerance.

Question 8

Q8. Why is a symmetrical tolerance preferable for process capability?

Answer 8

Allows variation on both sides of the mean

Reduces likelihood of scrap

Improves robustness against mean drift

Question 9

Q9. What is Six Sigma?

Answer 9

A9. A very demanding extension of TQM, focused on minimising variability and defects using statistical methods.

Question 10

Q10. What are the main objectives and distinguishing features of Six Sigma?

Answer 10

Objectives:

Identify and remove causes of defects

Minimise process variability

Achieve measurable improvements (cost, cycle time, pollution)

Key features:

Strong focus on customer needs

Decisions based on verified data (no guesswork)

Clear financial justification for every project

Strong management involvement

Structured roadmaps (e.g. DMAIC, DMADV)