Mastering Statistical Process Control : A Handbook for Performance Improvement Using SPC Cases

by Stapenhurst

• ISBN13: 9780750665292
• ISBN10: 0750665297
• Format: Paperback
• Copyright: 2005-06-21
• Publisher: Elsevier Science

Summary

Mastering Statistical Process Control shows how to understand business or process performance more clearly and more effectively. This practical book is based on a rich and varied selection of case studies from across industry and commerce, including material from the manufacturing, extractive and service sectors. It will enable readers to understand how SPC can be used to maximum effect, and will deliver more effective monitoring, control and improvement in systems, processes and management. The common obstacle to successful use of SPC is getting bogged down with control charts, forgetting that visual representation of data is but a tool and not an end in itself. Mastering SPC demonstrates how statistical tools are applied and used in reality. This is a book that will open up the power of SPC for many: managers, quality professionals, engineers and analysts, as well as students, will welcome the clarity and explanation that it brings to understanding the use and benefit of SPC in a wide range of engineering, production and service situations. Key case studies include using SPC to: Measure quality and human factors Monitor process performance accurately over long periods Develop best-practice benchmarks using control charts Maximise profitability of fixed assets Improve customer service and satisfaction * Shows how your business, process and profitability can benefit from process management and control * SPC is widely used and widely misunderstood. This is the only book to take an applications based approach to SPC * Ideal for managers, process engineers and quality personnel in both manufacturing and service sectors, as well as students of management, statistics, operations research, MBAs and Six Sigma candidates

Table of Contents

List of Figures	xi
List of Charts	xv
List of Case Studies and Examples	xx
Reference of Charts	xxii
Preface	xxv
Acknowledgements	xxvii
Introduction	xxix
The aim of the book	xxix
The structure of the book	xxx
How to use this book	xxxiii
Part 1 An Introduction to the Theory of SPC	1	(20)
Statistical process control	3	(18)
A word on processes	3	(1)
... And a word on variation	4	(1)
Some statistical measures	5	(2)
Why is understanding variation important to management?	7	(3)
Summary of the implications of process variation	10	(1)
Tampering (over-control) and its effect on performance	11	(3)
Control charts: the tool for understanding process performance	14	(2)
Dispelling some myths of SPC	16	(3)
Are there situations where SPC is not appropriate?	19	(1)
The relationship between SPC and Six Sigma	19	(1)
Summary	20	(1)
Part 2 Exploding Data Analysis Myths	21	(38)
Problems with monthly report tables, goals and quartiles	23	(14)
Introduction	23	(1)
Comparing pairs of numbers: a trap for the unwary	23	(2)
Death by numbers: the Saga of the monthly report	25	(2)
Who wins the prize? How not to compare regional performance statistics	27	(2)
Falsifying the data (and how to spot it): one result of setting targets	29	(3)
Querying the top quartile: Does it mean anything?	32	(4)
Summary	36	(1)
Exploring the mis-information in moving average charts	37	(10)
How they fail to respond to process changes, out-of-control points, trends and seasonality	37	(1)
Introduction	37	(1)
Analysis	38	(5)
Coping with seasonality and trends	43	(1)
What moving averages actually monitor	44	(2)
Summary	46	(1)
The problems with year-to-date figures	47	(12)
Introduction	47	(1)
Analysing YTD against plan	47	(3)
Analysing this year's YTD against last year's YTD	50	(2)
Why YTD charts do not work?	52	(1)
Analysing the YTD average	53	(1)
Comparing YTD and YTD average charts with control charts	54	(3)
Summary	57	(2)
Part 3 Putting SPC into Practice -- The Cases	59	(192)
The sources of the case studies	59	(1)
Control charts in the real worlds are not always so clear	60	(1)
A word on chart formats	60	(1)
Layout of and information in the case studies	61	(1)
How to use the case studies?	62	(1)
Investigating variation in chemical concentration	63	(6)
How control charts were used to identify, investigate and prove the cause of fluctuations in results	63	(6)
Improving examination results by analysing past performance and changing teaching methods	69	(6)
Demonstration that moving averages are poor indicators of true process performance	75	(10)
Monitoring the frequency of incidents	75	(10)
Monitoring rare events	85	(6)
How a sudden but uncertain change in safety record was shown to be significant	85	(6)
Comparing surgical complication rates between hospitals	91	(12)
Comparing the frequency of rare medical errors between centres	103	(16)
Metrics proposal for a training administration process	119	(14)
Reducing problems during borehole drilling	133	(8)
An example of monitoring two metrics on one chart	133	(8)
Applying control charts to benchmarking in the drilling industry	141	(12)
Comparing the results of using different charts to analyse a set of data	153	(12)
An application to a batch production process	153	(12)
Using control charts to analyse data with a trend	165	(10)
An application to cost management	165	(10)
Identifying a decrease in the use of hospitality suites	175	(12)
Increase in reject rate at manufacture due to inspectors' fear of losing their jobs	187	(8)
Comparison of test results of production process	195	(18)
From a batch production process to identify a key cause of variation and that the process is not capable of producing within specification	195	(18)
Categorising, de-seasonalising and analysing incident data using multivariate charts	213	(20)
Comparison of time-spent training across different facilities of an organisation	233	(18)
Part 4 Implementing and Using SPC	251	(124)
Understanding and interpreting a control chart	253	(10)
Introduction	253	(1)
The normal distribution and the standard deviation	253	(2)
The importance of the standard deviation	255	(1)
Definition of a process in a state of control	256	(1)
Interpreting a control chart	257	(3)
Possible causes of control chart signals	260	(1)
A note on the British and American control chart limits	260	(1)
Summary	260	(3)
Selecting the appropriate control chart	263	(14)
Introduction	263	(1)
Variables or attributes data?	263	(3)
Defects or defectives data?	266	(2)
Equal or variable size samples?	268	(1)
Choosing between the p and np chart	268	(1)
Choosing between the c and u chart	269	(1)
Choosing between X and X charts	270	(1)
Monitoring the mean and variability	271	(1)
Use of X/MR charts in place of c, u, np and p charts	272	(1)
Median and mid-range charts	272	(1)
Median moving range charts	273	(1)
Difference charts	273	(1)
Z charts	274	(1)
R or s charts?	274	(1)
Cumulative sum (cusum) charts	274	(1)
Selecting the most powerful chart	275	(1)
Summary	275	(2)
Procedures and formula for drawing control charts	277	(30)
Introduction	277	(1)
Frequency of measurements	278	(1)
Setting up charts	278	(1)
Part I Variables charts	279	(1)
The X/R charts	279	(7)
The s (standard deviation) chart	286	(1)
The median/R chart	287	(2)
Difference charts	289	(1)
Z charts	289	(1)
X/MR charts	290	(3)
Comments	293	(1)
Moving mean/moving range charts	293	(1)
Part 2 Attributes charts	294	(1)
p charts	294	(5)
np charts	299	(1)
c charts	300	(2)
u charts	302	(2)
Multivariate charts	304	(3)
An Introduction to cusum (cumulative sum) charts	307	(14)
Introduction	307	(1)
Basic cusum charts	307	(10)
Weighted cusum charts	317	(3)
Summary	320	(1)
Issues for the more advanced SPC users	321	(16)
Introduction	321	(1)
The number of observations required to identify a process change (average run length)	321	(5)
Identifying and dealing with non-normally distributed data	326	(2)
Identifying and dealing with auto-correlation	328	(1)
Dealing with rare events data	329	(1)
Analysing data in groups and subgroups	330	(6)
Summary	336	(1)
Data analysis tools	337	(16)
Introduction	337	(1)
Histograms	337	(6)
Run charts	343	(1)
Bar charts	344	(3)
Ranked bar charts and Pareto charts	347	(1)
Check sheets	348	(1)
Scatter diagrams	349	(2)
Summary	351	(2)
Setting up a processing monitoring system	353	(14)
Introduction	353	(1)
Deciding what to chart	354	(3)
Creating a framework for measurement	357	(2)
Collecting, charting, analysing and deciding on appropriate action	359	(5)
A word on process improvement	364	(2)
Summary	366	(1)
Potential process performance metrics	367	(8)
Introduction	367	(1)
The power of different chart types	367	(1)
A word on normalisation	368	(1)
Sample size/frequency of measurement	369	(1)
Outcome vs. process measures	369	(1)
Generic metrics applicable to a wide variety of organisations and sectors	370	(1)
Activity-specific metrics	371	(1)
Industry-specific metrics	371	(4)
Part 5 Developing SPC Skills: Organisational Review Questions, Workshops and Exercises	375	(46)
The Rods Experiment	377	(18)
A practical case study that can be used for training	377	(1)
Introduction	377	(2)
Data generation and collection	379	(1)
Check sheet	380	(1)
Histogram	380	(2)
Creating a run chart	382	(1)
Completing the X/MR control chart	383	(1)
Introducing the process change. Monitoring and analysing in real time	384	(3)
Drawing and interpreting an X/range chart	387	(2)
Drawing and interpreting a cusum chart	389	(2)
The difference chart	391	(1)
The Z chart	392	(2)
Comments	394	(1)
Organisational review questions, workshops and exercises	395	(10)
Reviewing what is happening in your organisation today	395	(1)
Selecting performance indicators	396	(1)
Selecting the correct control chart	397	(2)
Data workshops and case studies	399	(5)
Discussions	404	(1)
Answers to exercises in Chapter 30	405	(16)
Selecting the right control chart	405	(2)
Control chart interpretation	407	(1)
Downtime workshop	407	(1)
Repairs workshop	407	(3)
Days taken to raise invoices workshop	410	(1)
Blending workshop -- Part 1	410	(4)
Rejected tenders	414	(1)
Surgical complications	415	(6)
Part 6 An Introduction to Six Sigma Luis Miguel Gimenez	421	(18)
An Introduction to Six Sigma	423	(16)
Introduction	423	(1)
What is Six Sigma?	423	(1)
The basis of Six Sigma	424	(1)
The three key roles in Six Sigma: Management, Specialists and Staff	424	(1)
The meaning of quality in Six Sigma	424	(1)
The two key measures in Six Sigma	425	(1)
Selecting improvement projects	425	(1)
The Six Sigma improvement methodology	425	(14)
Bibliography, references and other resources	439	(2)
Experimental Resources	441	(2)
Appendix A	443	(2)
Glossary of terms and symbols	445	(10)
Index	455