1. Chapter 201 Statistical Techniques for Achieving Quality Chapter 20 Achieving Quality Through Continual Improvement Claude W. Burrill / Johannes Ledolter Published by John Wiley & Sons, Inc., 1999 Prepared by Dr. Tomi Wahlström, University of Southern Colorado

2. Chapter 202 Introduction b Statistical quality control is a branch of applied statistics dealing with statistical tools that help control the quality of products and improve the processes responsible for these products b Acceptance sampling plans rely on samples of incoming or outgoing material to decide whether a lot should be accepted

3. Chapter 203 Introduction b Control charts are important tools for monitoring processes through the products they produce b Statistical design of experiments and experimentation may also be used as a part of statistical quality control

4. Chapter 204 Sample Inspection b When it is not realistic to use census for inspection, one must rely on sample inspection Taking a small sample size n from each shipment lot, inspecting the sampled items, and counting the number of items meeting the requirementsTaking a small sample size n from each shipment lot, inspecting the sampled items, and counting the number of items meeting the requirements

5. Chapter 205 Control Charts b Graphical tool used to understand the production process and to help assure that the quality of products produced by that process is consistent (or stable) over time b Easy to explain and apply Raise important issues and force their resolutionRaise important issues and force their resolution Focus attention on process rather than productFocus attention on process rather than product

6. Chapter 206 X-bar Charts b Also known as the mean chart b Used in situations where one measures a continuous variable b Terms associated with it: Upper and lower control limitsUpper and lower control limits Stable process, constant cause systemStable process, constant cause system Assignable causeAssignable cause

7. Chapter 207 R-Charts b Also known as the range chart b Plots the ranges of samples taken over time and monitors the variability of the process over time b Both X-bar and R-charts are used whenever we measure so called “variable” aspects of a process

8. Chapter 208 Control Charts for Attribute Data b p-Charts Used to monitor the proportion of defective itemsUsed to monitor the proportion of defective items b c-Charts Used to keep track of the number of defects or flaws on a productUsed to keep track of the number of defects or flaws on a product b Both used for attribute data Data that describes the presence or absence of a certain characteristicData that describes the presence or absence of a certain characteristic

9. Chapter 209 Process Capability b Typically, a product must meet certain specifications called a target value (Tg), lower specification limit (LSL), and an upper specification limit (USL) b If the products meet the specifications, the process is capable of producing according to the given specifications Capability Index (Cp)

10. Chapter 2010 Statistical Design of Experiments b Information can be collected in an active or passive manner and must be collected according to an experimental plan b Important principles to consider: RandomizationRandomization BlockingBlocking –“Block whatever you can block, and randomize whatever you can’t block.”

11. Chapter 2011 Questions?

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