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Chapter 21D. Quality Tools and TechniquesDefine and use various problem-solving andcontinuous improvement tools, including theseven quality control tools, plan–do–check–act (PDCA)/plan–do–study–act (PDSA),Six Sigma DMAIC, root cause analysis, etc.(Application)Body of Knowledge IV.DPart IV.DUnderstanding of basic problem-solving and continuous improvement tools andtechniques is critical for a quality inspector to be effective and to function withinthe larger quality community. It has been said many times that as many as 85percent of the problems encountered in production or service delivery operationscan be solved with these basic tools and techniques. We will begin our discussionwith the seven quality control tools, proceed with a discussion of PDCA/PDSA, and conclude with a discussion of the DMAIC and root cause analysistechniques.SEVEN BASIC QUALITY CONTROL TOOLSThis seven basic quality control tools (plus two variants) consist of the following:1. Histogram2. Stem-and-leaf diagram3. Scatter diagram4. Run chart (also, known as line graph or time series graph)5. Check sheet6. Pareto chart7. Cause-and-effect diagram (also known as fishbone orIshikawa diagram)314

Chapter 21: D. Quality Tools and Techniques 3158. Defect concentration diagram9. Control charts*These basic tools form a simple but very powerful structure for quality improvement.Once inspectors, technicians, and operators/service delivery personnelbecome fully familiar with these tools, management must get involved to sustaintheir use in an ongoing quality improvement process. Management must createan environment where these tools become part of day-to-day production or serviceprocesses. Implementation of these tools without management’s commitmentportends the impending failure of continuous improvement efforts. Thus, besidesdiscussing these tools we will also explore here some of the questions that arisewhile implementing the tools.Every job, whether in a manufacturing company or in a service company,involves a process. As described, each process consists of a certain number of steps.No matter how well the process is planned, designed, and executed there is alwayssome potential for variability. In some cases this variability may be very littlewhile in other cases it may be very high. If the variability is very little then it isusually caused by common causes, which are unavoidable and can’t be controlled.If the variability is very high then we expect that besides the common causes thereare some other causes, usually known as assignable causes, present in the process.Any process working under only common causes or chance causes is consideredto be in statistical control. If a process is working under both common and assignablecauses then the process is considered unstable, or not in statistical control.PLAN–DO–CHECK–ACT (PDCA)/PLAN–DO–STUDY–ACT(PDSA) CYCLEThe PDCA and the PDSA cycles are very common in use and in the language ofthe quality profession. Accordingly, we begin our discussion of these two cycleswith a clarification. That clarification is that these two cycles were not created bythe same person, the two cycles are not structurally the same, and that the twocycles have different philosophical intents. As has been documented by McKinley(2006), the original creators of the cycles were as follows:• Walter Shewhart—Shewhart cycle—PDCA. Development date: late1930s. It should be noted that Shewhart is credited with the “Shewhartcycle.” However, Shewhart did not label the steps of his cycle asPDCA, but rather used the terms specification, production, andinspection.• W. Edwards Deming—Deming cycle—PDSA. Development date: late1950s. Structurally, these cycles differ on the “check” step advocatedby Shewhart as compared to the “study” step advocated by Deming.Part IV.D* A detailed discussion of the basic quality control tools has been presented in Chapters 18and 19 of this book; so the discussion will not be repeated here to avoid duplication.

Chapter 21

D. Quality Tools and Techniques

Define and use various problem-solving and

continuous improvement tools, including the

seven quality control tools, plan–do–check–

act (PDCA)/plan–do–study–act (PDSA),

Six Sigma DMAIC, root cause analysis, etc.

(Application)

Body of Knowledge IV.D

Part IV.D

Understanding of basic problem-solving and continuous improvement tools and

techniques is critical for a quality inspector to be effective and to function within

the larger quality community. It has been said many times that as many as 85

percent of the problems encountered in production or service delivery operations

can be solved with these basic tools and techniques. We will begin our discussion

with the seven quality control tools, proceed with a discussion of PDCA/

PDSA, and conclude with a discussion of the DMAIC and root cause analysis

techniques.

SEVEN BASIC QUALITY CONTROL TOOLS

This seven basic quality control tools (plus two variants) consist of the following:

1. Histogram

2. Stem-and-leaf diagram

3. Scatter diagram

4. Run chart (also, known as line graph or time series graph)

5. Check sheet

6. Pareto chart

7. Cause-and-effect diagram (also known as fishbone or

Ishikawa diagram)

314

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