Module 3:

1. Operations Management as a Competitive Weapon Module 3: Statistical Quality Control

2. OM Course Framework 3. Dependability - Project Management - JIT 1. Cost - Design & Selection 4. Flexibility - Inventory - Supply Chain - Location - Forecasting - Aggregate Planning 2. Quality - TQM - SQC

3. Learning Objectives At the end of this module, each student will be able to: • Discuss SQC background • Discuss SQC types and characteristics • Explain Statistical Process Control Module 03: Statistical Quality Control

4. 1. SQC Background • Involves collecting, organizing, & interpreting data • Objective: Regulate product quality • Used to • Control the process as products are produced • Inspect samples of finished products Module 03: Statistical Quality Control

5. Statistical Quality Control Process Acceptance Control Sampling Variables Attributes Variables Attributes Charts Charts 2. SQC Types Module 03: Statistical Quality Control

6. Attributes Characteristics for which you focus on defects Classify products as either ‘good’ or ‘bad’, or count # defects e.g., radio works or not Variables Characteristics that you measure e.g., weight, length Whole number or fractional value 2. SQC Characteristics

7. 3. Statistical Process Control Statistical Quality Control Process Acceptance Control Sampling Variables Attributes Variables Attributes Charts Charts Module 03: Statistical Quality Control

8. Statistical Process Control (SPC) • Statistical technique used to ensure process is making product to standard • All process are subject to variability • Natural causes: Random variations • Assignable causes: Correctable problems • Machine wear, unskilled workers, poor mat’l • Objective: Identify assignable causes Module 03: Statistical Quality Control

9. 95.5% of allX fall within ± 2X Control Charts-Theoretical Basis Module 03: Statistical Quality Control

10. Control Charts-Theoretical Basis

11. Control Charts-Theoretical Basis

12. Control Charts-Theoretical Basis UCL LCL

13. Control Chart Purposes • Show changes in data pattern • e.g., trends • Show causes of changes in data • Assignable causes • Natural causes Module 03: Statistical Quality Control

14. SQC Types Statistical Quality Control Process Acceptance Control Sampling Variables Attributes Variables Attributes Charts Charts Module 03: Statistical Quality Control

15. R Chart • Shows sample ranges over time • Difference between smallest & largest values in inspection sample • Monitors variability in process • Example: Weigh samples of coffee & compute ranges of samples; Plot Module 03: Statistical Quality Control

16. X Chart • Shows sample means over time • Monitors process average • Example: Weigh samples of coffee & compute means of samples; Plot Module 03: Statistical Quality Control

17. SQC Types Statistical Quality Control Process Acceptance Control Sampling Variables Attributes Variables Attributes Charts Charts Module 03: Statistical Quality Control

18. p Chart • Type of attributes control chart • Shows % of nonconforming items • Example: Count # defective chairs & divide by total chairs inspected; Plot • Chair is either defective or not defective Module 03: Statistical Quality Control

19. c Chart • Type of attributes control chart • Shows number of nonconformities (defects) in a unit • Example: Count # defects (scratches, chips etc.) in each chair of a sample of 100 chairs; Plot Module 03: Statistical Quality Control