Quality Management Tools

1. Quality Management Tools 393SYS

2. 1 Modern Quality Management • Modern quality management • requires customer satisfaction • prefers prevention to inspection • recognizes management responsibility for quality • Noteworthy quality experts include Deming, Juran, Crosby, Ishikawa, Taguchi, and Feigenbaum • Quality; Who’s who 393SYS

3. Quality Experts • Deming was famous for his work in rebuilding Japan and his 14 points • Juran wrote the Quality Control Handbook and 10 steps to quality improvement • Crosby wrote Quality is Free and suggested that organizations strive for zero defects • Ishikawa developed the concept of quality circles and using fishbone diagrams • Taguchi developed methods for optimizing the process of engineering experimentation • Feigenbaum developed the concept of total quality control 393SYS

4. Fishbone or Ishikawa Diagram 393SYS

5. Malcolm Baldrige Award and ISO 9000 • The Malcolm Baldrige Quality Award was started in 1987 to recognize companies with world-class quality • ISO 9000 provides minimum requirements for an organization to meet their quality certification standards • HKMA Quality Award http://www.hkma.org.hk/qa/award.htm 393SYS

6. 2. Quality Planning • It is important to design in quality and communicate important factors that directly contribute to meeting the customer’s requirements • Design of experiments helps identify which variables have the most influence on the overall outcome of a process • Many scope aspects of IT projects affect quality like functionality, features, system outputs, performance, reliability, and maintainability 393SYS

7. Quality Assurance • Quality assurance includes all the activities related to satisfying the relevant quality standards for a project • Another goal of quality assurance is continuous quality improvement • Benchmarking can be used to generate ideas for quality improvements • Quality audits help identify lessons learned that can improve performance on current or future projects 393SYS

8. Quality Control • What it is: • *** • The main outputs of quality control are • acceptance decisions • rework • process adjustments • Some tools and techniques include • pareto analysis • statistical sampling • quality control charts • testing 393SYS

9. 3. Pareto Analysis • Pareto analysis involves identifying the vital few contributors that account for the most quality problems in a system • Also called the 80-20 rule, meaning that 80% of problems are often due to 20% of the causes. It is the fundamental postulates underlie the rational for the Statistical SW Quality Assurance. • Pareto diagrams are histograms that help identify and prioritize problem areas. 393SYS

10. 80% of the contribution comes from 20% of the contributors:- • 80% of the engineering is consumed by 20% of the requirements • 80% of the software cost is consumed by 20% of the components • 80% of the errors are caused by 20% of the components • 80% of software scrap and rework is caused by 20% of the errors • 80% of the progress is made by 20% of the people. • … 393SYS

11. Sample Pareto Diagram 393SYS

12. Statistical SQA • SQA & Traceability as example on SQA & FTR notes L14 • p209, Pressman. 393SYS

13. Statistical Sampling and Standard Deviation • Statistical sampling involves choosing part of a population of interest for inspection • The size of a sample depends on how representative you want the sample to be • Sample size formula: Sample size = .25 X (certainty Factor/acceptable error)2 393SYS

14. Commonly Used Certainty Factors 95% certainty: Sample size = 0.25 X (1.960/.05)2 = 384 90% certainty: Sample size = 0.25 X (1.645/.10)2= 68 80% certainty: Sample size = 0.25 X (1.281/.20)2 = 10 393SYS

15. Standard Deviation • Standard deviation measures how much variation exists in a distribution of data • A small standard deviation means that data cluster closely around the middle of a distribution and there is little variability among the data • A normal distribution is a bell-shaped curve that is symmetrical about the mean or average value of a population 393SYS

16. Normal Distribution and Standard Deviation 393SYS

17. Sigma and Defective Units 393SYS

18. Quality Control Charts and the Seven Run Rule • A control chart is a graphic display of data that illustrates the results of a process over time. It helps prevent defects and allows you to determine whether a process is in control or out of control • The seven run rule states that if seven data points in a row are all below the mean, above the mean, or increasing or decreasing, then the process needs to be examined for non-random problems 393SYS

19. Control Chart of 12” ruler 393SYS

20. Control Chart contiu. • The output of a production process will fluctuate. The causes of fluctuation can just be random or non-random due to desirable/undesirable process change. Control charts graph and measure process data against control limits. Control charts can distinguish the random variation from assignable causes or non-random causes. • We cannot adjust random variation out of a process. Process adjustments for random variation are neither necessary nor desirable. This is over-adjustment or tempering, and it makes the process worse. • We can and must investigate assignable causes (or non-random causes). Points outside the control limits are evidence of process problems. Analyst must investigate every out of control point for an assignable cause. They must record their findings and any corrective actions. For example, a tool adjustment, or change in Formal Technical Review format or worn tooling, may correct the problem. 393SYS

21. Pattern analyzing of Control Chart 7-Run rule 7-run-rule is used to filter out the random variation in a production process. shows the ‘trends’ that are caused by the ‘assignable causes’ or non-random causes that required investigation and possible corrective action to be taken. 7-run-rule pattern: • seven points above mean value; • seven points below mean value; • seven points or all increasing ; or • seven points all decreasing the patterns are indicators of non-random problems which can be symptom of process out of control. 393SYS

22. To develop a Control Chart to determine project stability • Plot individual metric values on a chart. • Compute the mean value for the metrics value and plot the line. • Plot the Upper Control Limit and Lower Control Limit. • Compute a standard deviation as (Upper-control-limit - mean)/3. Plot lines one and two standard deviation above and below Am. If any of the standard deviation lines is less than 0.0, it need not be plotted unless the metric being evaluated takes on values that are less than 0.0. • The Std Dev.# is then plotted on the control chart. 393SYS

23. Statistical Testing Statistical testing is a system testing process in which the objective is to measure the reliability of a system rather than to discover faults. Statistical testing can be combined with reliability growth modeling. Predictions of the final system reliability and when that will be achieved can be made. As failures are discovered, the underlying faults causing these failures are repaired so that the reliability of the system can improve in the course of the testing process A lot of airlines manage dispatch reliability with statistical testing approach. 393SYS

24. The Cost of Quality • The cost of quality is • the cost of conformance or delivering products that meet requirements and fitness for use • the cost of nonconformance or taking responsibility for failures or not meeting quality expectations 393SYS

25. Total Quality Cost • Price of nonconformance PONC • Price of Conformance (POC) • peer walkthroughs, inspections • development & impl. QMS, standards, training • setting up & running of quality program • Cost of Quality (COQ) = POC + PONC 393SYS

26. Costs Per Hour of Downtime Caused by Software Defects 393SYS

27. Five Cost Categories Related to Quality • Prevention cost: the cost of planning and executing a project so it is error-free or within an acceptable error range • Appraisal cost: the cost of evaluating processes and their outputs to ensure quality • Internal failure cost: cost incurred to correct an identified defect before the customer receives the product • External failure cost: cost that relates to all errors not detected and corrected before delivery to the customer • Measurement and test equipment costs: capital cost of equipment used to perform prevention and appraisal activities 393SYS

28. Organization Influences, Workplace Factors, and Quality • Study by DeMarco and Lister showed that organizational issues had a much greater influence on programmer productivity than the technical environment or programming languages • Programmer productivity varied by a factor of one to ten across organizations, but only by 21% within the same organization • Study found no correlation between productivity and programming language, years of experience, or salary • A dedicated workspace and a quiet work environment were key factors to improving programmer productivity 393SYS