Quality Control

Cornelius Koo

W. Edwards Deming

Quality: a definition

• “The degree to which a set of inherent characteristics fulfills requirements.”

– Andy Crowe, PMP. The PMP Exam, How to Pass On Your First Try 5th ed.

Normal Distribution Curve

Six Sigma (Std Dev)

σ value

1σ 0.682689492137

2σ 0.954499736104

3σ 0.997300203937

4σ 0.999936657516

5σ 0.999999426697

6σ 0.999999998027

7 Basic Tools of Quality Control

1. Fishbone Diagram

2. Checksheet

3. Histogram

4. Pareto Chart

5. Scatter Diagram

6. Control Chart

7. Flow Chart

1. Fishbone Diagram(Ishikawa, Cause-Effect Diagram)

2. Checksheet

3. Histogram

4. Pareto Chart

Pareto Chart

5. Scatter Diagram(Correlation Chart)

6. Control Chart

Out of Control

• The process is out of state of statistical control under these two circumstances :

1. A data point falls outside the upper or lower control limit.

2. There are nonrandom data points; may happen within the upper and lower control limits.

Rule of Seven

• Refer to a group or series of nonrandom data points that total seven on one side of the mean.

• It tells you that although none of these points are outside of the control limits, they are not random and the process is out of control.

• Should investigate this type of situation and find a cause.

Assignable Cause/Special Cause Variation

• Signifies that a process is out of control.

• It means a data point or series of data falls outside the control limits and requires investigation to determine the cause of variation.

• We can use the cause and effect diagram to try uncover the root cause of the variation.

7. Flowchart