Quality Management (PQM01) Chapter 04 - Quality Control

Transcription

1 Quality Management (PQM01) Chapter 04 - Quality Control

2 Slide 1

3 Slide 2 Involves monitoring specific project results to determine if they comply with relevant quality standards, and identifying ways to eliminate causes of unsatisfactory results. Performed throughout the project Results in ability to eliminate or reduce causes of unsatisfactory performance 2

4 Slide 3 Juran defines Quality Control as The process through which we measure quality performance, compare it with quality goals, and act on the difference. 3

5 Slide 4 Cost of Quality Conformance Nonconformance Prevention Planning Scrap Failure Appraisal Training Rework Auditing Testing Controlling Expediting Warranty Service Recalls v Copyright and all rights reserved 4

6 Slide 5 7 Basic Quality Tools Also know as 7QC Tools. Used within PDCA cycle to solve quality problems. They are: Cause-and-effect diagrams Checksheets Histograms Flowcharts Pareto diagrams Control charts Scatter diagrams v Copyright and all rights reserved 5

7 Slide 6 Key Concepts Prevention vs. Control Prevention Aims to stop an event or failure from ever occurring Control Attempts to limit the impact of a failure after it has happened 6

8 Slide 7 Key Concepts Attribute Sampling & Variable Sampling Attribute Sampling Asks the question, does the attribute exist and is binary in nature? Variable Sampling Addresses characteristics like how much and is numeric in nature 7

9 Slide 8 Key Concepts Special Causes vs. Random Causes Special Causes Unusual events Random/Common Causes Normal or expected variations 8

10 Slide 9 Key Concepts Tolerances & Control Limits Tolerances Range of acceptable results Control Limits Values that indicate if a process is in control 9

11 Slide 10 Trend Analysis Involves using mathematical techniques to forecast future outcomes based on historical results. Technical Performance how many errors or defects have been identified, how many remain to be corrected? Cost and Schedule Performance how many activities per period were completed with significant variances? 10

12 Slide 11 A Good Quality System Will Compare actuals to standards (inspection) Act when standards are not met Plan for improvements 11

13 Slide 12 Control Charts Graphic display of the results of a process over time Based on statistical probability Determine if a process is in control Verify the impact on a process when changes are made 12

14 Slide 13 Control Charts Key Terms A center line - designated with an x, which provides the average (x) of the process area. An upper line designating the upper control limit (UCL). 13

15 Slide 14 Control Charts Key Terms The lower line designating the lower control limit (LCL) Points outside of the UCL and LCL are indicative that the process is out of control and/or unstable 14

16 Slide 15 In Control When in control a process should not be adjusted UCL X LCL x x x x x x x x x x x What is out of control? x 3ơ 2ơ 1ơ -1ơ -2ơ -3ơ The rule of 7? 15

17 Slide 16 Variations Normal Common, random, naturally occurring Found throughout the entire system Accounts for 85% of variation (Deming) Management s responsibility to correct Requires investigation and elimination or incorporation 16

18 Slide 17 Variations Abnormal Assignable or special Specific to material, machinery, manpower, or method Accounts for only 15% of variation Location supervisor or worker should correct 17

19 Slide 18 SIPOC Sometimes called COPIS Tool that summarizes the inputs and outputs of one or more processes in table form. Acronym SIPOC stands for suppliers, inputs, process, outputs, and customers which form the columns of the table. First used in TQM programs. Used today in Six Sigma and Lean manufacturing. v Copyright and all rights reserved 18

20 Slide 19 SIPOC Supplier Input Process Output Customer Requirements & Feedback Loop Requirements & Feedback Loop Requirements List Measurements List Requirements List Measurements List v Copyright and all rights reserved 19

21 Slide 20 Pareto Diagrams A histogram, ordered by frequency of occurrence, that shows how many results were generated by type of category of identified cause

22 Slide 21 Pareto Diagrams Can combine bar charts with Pareto Diagrams Cumulative 75 Percentage Improper Rotation Noise Wobble Pressure Axle Caulking Case Wobbles Other Number of Defective Cases Percentage of Defective Cases Car Problems 21

23 Slide 22 Statistical Sampling Terms Attribute Either accept or reject (% defective) Variable Anything measured (average measure) Producer s Risk (alpha) chance of rejecting a good lot. Type II error. 22

24 Slide 23 Statistical Sampling Terms Consumer s Risk (Beta) chance of accepting a bad lot. Type I error. Sampling Plan Sample size (n) and acceptance criteria ( c ) 23

25 Slide 24 Acceptance Sampling Process of evaluating a portion of the product in a lot for the purpose of accepting or rejecting the entire lot. Alternative to 0% or 100% inspection Single or multiple samples 24

26 Slide 25 Advantages of Acceptance Sampling Smaller inspection staff Less product damage Quicker decisions Less inspection errors Lower cost 25

27 Slide 26 Disadvantages of Acceptance Sampling Sampling risks Less information 26

28 Slide 27 Quality Circles 5-15 workers who meet on a frequent basis to identify, discuss and solve productivity and quality problems One member of the group acts as the liaison between management and the group 27

29 Slide 28 Quality Assurance Applying the planned systematic quality activities to ensure that the project employs all processes needed to meet requirements. Quality Control Monitoring specific project results to determine whether they comply with relevant quality standards, and identifying ways to eliminate causes of unsatisfactory performance 28

30 Slide 29 Quality Planning Perform Quality Assurance Continuous Improvement Perform Quality Control 29

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32 Review Questions: 1. Which of the following statements concerning quality control is NOT true? A. Quality control involves monitoring specific project results to determine if they comply with relevant quality standards, and identifying ways to eliminate causes of unsatisfactory results B. Quality control is performed throughout the project C. Quality control results in the ability to eliminate or reduce causes of unsatisfactory performance D. None; all of the above are true 2. Which of the following best describes the preventive aspect of quality control? A. It attempts to limit the impact of a failure after it has happened B. It aims to stop an event or failure from ever occurring C. All of the above D. None of the above 3. What type of sampling asks the question "does the attribute exist", and is binary in nature? A. Attribute sampling B. Variable sampling C. Both of the above D. None of the above 4. When evaluating the causes of errors, what type explains outcomes that are naturally occurring? A. Type I errors B. Type II errors C. Random causes D. Special causes 5. What term is used to describe the range of acceptable results? A. Control limits B. Tolerances C. Special causes D. Random causes

33 6. Who describes quality control as the process through which we measure quality performance, compare it with quality goals, and act on the difference? A. Deming B. Crosby C. Juran D. Taguchi 7. What type of analysis involves using mathematical techniques to forecast future outcomes based on historical results? A. Technical analysis B. Trend analysis C. Performance analysis D. None of the above 8. What kind of performance evaluates how many errors or defects have been identified, or how many remain to be corrected? A. Technical performance B. Cost and schedule performance C. Technical analysis D. Trend analysis 9. Which of the following will a good quality control system do? A. Compare actuals to standards (inspection) B. Act when standards are not met C. Plan for improvements D. All of the above 10. Which of the following is used to describe a control chart? A. Based on statistical probability B. Determine if a process is in control C. Verify the impact on a process when changes are made D. All of the above 11. Which of the following is NOT a common name for the curve most often used to describe a variable that is unaffected by other variables? A. A normal distribution B. A bell curve C. A standard distribution D. A Gaussian distribution

34 12. Which of the following terms is often used to describe the mid-point of the distribution when examining a control chart? A. The mean B. X (with a line above it) C. The centerline D. All of the above 13. Which of the following terms is often used to describe the maximum allowable value for a control chart? A. Lower control limit B. Upper control limit C. Maximum value D. Top value 14. Which of the following is NOT a term used to describe variations that account for 85% of the error? A. Normal variation B. Standard variation C. Type II errors D. Abnormal variation 15. A graph ordered by frequency of occurrence that shows how many results were generated by type of category of identified cause is called what? A. A histogram B. A pareto diagram C. A trend chart D. A scatter diagram 16. Which of the following statistical sampling terms is used to describe a tested item that is either accepted or rejected? A. A variable B. A sample plan C. An attribute D. None of the above

35 17. What kind of risk is involved when you are worried that you might accept product that should be rejected? A. Producer risk B. Consumer risk C. Project risk D. Alpha risk 18. Which of the following is an advantage of acceptance sampling? A. Less product damage B. Quicker decisions C. Less inspection errors D. All of the above 19. Which of the following is NOT a characteristic of a quality circle? A. It is usually made up of 5-15 workers B. The team meets on a frequent basis to identify, discuss, and solve productivity and quality problems C. One member of the group acts as the liaison between management and the group D. All of the above are characteristics of a quality circle 20. Which of the following statements defines quality control? A. It is the application of planned systematic quality activities to ensure that the project employs all processes needed to meet requirements B. It is the monitoring of specific project results to determine whether they comply with relevant quality standards, and identifying ways to eliminate causes of unsatisfactory performance C. Both statements define quality control D. Neither statement defines quality control 21. In which of the following processes is continuous improvement most commonly categorized? A. Quality planning B. Perform quality assurance C. Perform quality control D. All of the above

36 Answer Key: 1. D Quality control involves monitoring specific project results to determine if they comply with relevant quality standards, and identifying ways to eliminate causes of unsatisfactory results. It is performed throughout the project and results in the ability to eliminate or reduce causes of unsatisfactory performance. 2. B Prevention, as a concept in quality management, is all about stopping an event or failure from ever occurring within the project. 3. A Attribute sampling and variable sampling are the two types of sampling techniques. Attribute sampling asks if the attribute exists at the desired level or value. It is a simple yes or no question. 4. C Random causes are inherent in nature and are difficult to predict. However, they account for only 85% of the errors. 5. B Tolerances describe the limits and what you are willing to tolerate or accept, in terms of the results. 6. C Juran describes quality control as the process through which we measure quality performance, compare it with quality goals, and act on the difference. 7. B Trend analysis takes past values and using mathematical techniques forecasts future outcomes based on historical trends. 8. A Technical performance is a purely quantitative method for measuring results. It focuses on how many defects have been identified and keeping track of how many remain to be corrected.

37 9. D By definition, according to Juran, a good quality control system will measure quality performance, compare it with quality goals, act on the difference, and plan for improvements. 10. D A control chart is based on statistical probability and is used to determine if a process is in control by establishing upper and lower control limits. It can also verify the impact on a process when changes are made. 11. C The curve that describes any independent variable with a nominal number of cases that is distributed in a balanced or normal fashion is called a normal distribution, a bell curve or a Gaussian distribution. 12. D It is most commonly referred to as the mean of the distribution; it can also be represented by an X with a line over it, or called the centerline of the distribution. 13. B Within a control chart, the tolerances are defined by an upper and lower control limit. These create the maximum and minimum allowable value. 14. D Abnormal variation, assignable, or special variations account for only 15% of differences and require the resource to take action. These are different than the normal or standard variation that is also referred to as a type II error. 15. B A pareto diagram is a bar chart representing occurrences of something, usually errors. It is typically organized from left to right with the most commonly occurring errors on the left. 16. C An attribute is a variable that has a yes or no answer. It can be binary in nature or it can be a target value that must be reached as a minimum. 17. B Consumer risk is sometimes referred to as a type I error and represents the likelihood of accepting a product that should be rejected.

38 18. D Acceptance sampling allows the organization to test only a small portion of the total products. This allows for less damage (e.g. fewer products tested), quicker decisions, and fewer errors. 19. D Quality circles are usually made up of 5-15 workers, require the team to meet on a frequent basis to identify, discuss, and solve productivity and quality problems. They often require that one member of the group acts as the liaison between management and the group. 20. B Quality control is the monitoring of specific project results to determine whether they comply with relevant quality standards, and identifying ways to eliminate causes of unsatisfactory performance. 21. B Continuous improvement is part of the perform quality assurance process.