Chapter 7 Quality Tools. Which tool is best? Tools can serve as the backbone for virtually any type of quality improvement effort (Six Sigma, TQM, 8D)

Chapter 7

Quality Tools

Which tool is best?

• Tools can serve as the backbone for virtually any type of quality improvement effort (Six Sigma, TQM, 8D)

• Graphical representations of data help us understand the true importance of data.

• There is no single one-size fits all solution. Every project and problem is different.

Diagnostic Tools

• Graphical Tools:– Histogram– Boxplots– Probability distribution plots– Main-effects plots– Pareto charts– Run charts– Multi-Vari charts– Time-series plots– Scatter plots

• Analytical Tools:– Cause-Effect (CE) diagram– Failure mode-effects Analysis

(FMEA)– XY matrix– Affinity diagram– Fault tree analysis (FTA)

Diagnostic Tools

• Graphical Rep. of Process:– Process flow charts– Process mapping– Cross-functional mapping– Deployment diagram– Supplier-input-process-

output-customer (SIPOC) diagram

– Input-process-output (IPO) diagram

– Force-field analysis

• Other Tools:– Checksheets– Scorecards

Problem Definition

• A good problem definition will include quantified information about the problem, the magnitude of the problem, the baseline, and the gap remaining to reach a benchmark or desired state– Be Specific

– Use declarative format

– Quantify

– Be factual

• Example of poor problem definition: “Reduce restorable time for severity 1 telephone banking problems, focusing on human errors as root cause”

• Example of good problem definition: “Reduce restorable time from 51% per month for severity 1 telephone banking problems to 30% or less per month by the third quarter of this year, resulting in annual savings of $4.5M”

Y = f (x)

• The transfer equation of Y=f(x) where X =x1, x2, x3,…,xn recognizes that a causal relationship exits in any process of action performed.

• Y is a function of one or many x’s where Y is the dependent variable and the x’s are independent variables.

• X can equal quality, delivery time, cost of the product. Therefore Critical to Satisfaction refers to any variable that has significant influence on one of more of the determinants of customer satisfaction.

» Pareto principal suggests that 80% of the of the total error or variance will be caused by 20% of the variables. These are the “vital few”, while the remaining are the “trivial many”. The key is to identify these vital few.

x1 x2 x3 . . . . xn

Uncontrollable variables or factors (noise)

Inputs ProcessProcess

. . .

Critical-to (CT) Definitions

• Critical-to-Satisfaction (CTS) characteristics – expression of the customer’s vital needs.• Critical-to-Quality (CTQ) characteristics- the product, service and/or transactional

characteristics that significantly influence one or more CTS in terms of quality.• Critical-to-Delivery (CTD) characteristics- “ “ “ “ in terms of delivery. • Critical-to-Cost (CTC) characteristics- “ “ “ “ in terms of cost.

• Critical-to-Process (CTP) characteristics- Process parameters that significantly influence a CTQ, CTD, and/or CTC.

Variables (X)

The Leverage Principle

• Not all X variable affect the outcome (Y) equally. • In Six Sigma process:

• Identify the variables that exert strong influence (Vital Few).• Then we must focus on controlling these variables. Design of

Experiments (DOE) is used to achieve this objective.

The Leverage Principle(Variation Reduction Strategies)

Strategy 1 2 3 4 5 6Total Red.

EffortsTotal % Impr.

Baseline 4 11 3 2 1 1 -- 12.33

Reduce each by 1 3 10 2 1 0 0 6 10.68 13.4%

Eliminate all but one 0 11 0 0 0 0 11 11.00 10.8%

Reduce the vital one 4 8 3 2 1 1 3 9.75 20.9%

6

1

2

jjTotal

What does measurement mean?

• Concept of measurement: seek to compare or contrast a physical attribute of something to a rational and invariant standard performance gap

• Seek to quantify such gaps for purposes of communications, verification, and analysis.

• Measure subjective matter (customer satisfaction) through surveys, questionnaires

• Measure physical characteristics, time characteristics, defect rates….

How do we know if customers are happy?Goal is to understand how to better satisfy the customer

• Survey design considerations:– Length (not too long)– Appearance (simple, not busy)– Types of questions (statements of fact or measures of performance or importance)

• Types of question formats:– Closed-ended (yes/no)– Rating scales– Open-ended questions / probes

• Other considerations:– Focus on one theme– Usually best to include a midpoint in rating scales (i.e. odd number)– Try to solicit feelings toward your competitors.

• Identify specific target control groups:– At least 10% of customer base– Stratify various customer segments– Give prior notice, before delivering survey– Personalize the survey and cover letter– Address confidentiality– Offer an incentive or token of appreciation for completion

– Follow up with a friendly collection strategy– Develop action plans that are based on

results– Communicate results to customers– Follow up with repeat surveys to monitor

changes over time

Likert scale

• A subjective scoring system that allows a person being surveyed to quantify likes and preferences on a 5-point scale, with 1 being the least important, relevant, interesting, or other, and 5 being most excellent, important, etc

• Strongly Agree / Agree / Undecided / Disagree / Strongly Disagree• Very Frequently /Frequently /Occasionally /Rarely /Very Rarely /Never• Very Important / Important / Moderately Important / Of Little Importance /

Unimportant• Excellent / Above Average / Average / Below Average /Extremely Poor • Almost Always True / Usually True / Often True / Occasionally True /

Sometimes But Infrequently True / Usually Not True / Almost Never True

Continuous Scales• Linear Scale: A scale with equal

divisions for equal values

• If the data are nonlinear (i.e., with a very wide range of values), then a logarithmic scale (in this case base 10) may be more appropriate.

Analytical Tool: Cause-Effect (CE) Analysis

• CE diagram (fishbone diagram) uses collective knowledge to identify the main causes (x) of the effect (y) under study.– Manufacturing diagrams (Six M’s: measurement, manpower,

machines, materials, methods, and mother nature).– Transactional diagrams (4 P’s :Policies, procedures, personnel,

environment).

• Graphical way to show relationships between inputs and outputs.

• Label each cause with a “C” (fixed variable), “N” (Noise) or “X” (experimental independent variable.)

• CE Diagrams can be constructed using MINITAB (page 156-157)

Cause-Effect (CE) Analysis

www.syncfusion.com/.../img/Fishbone_larger.png

Analytical Tool: Failure Mode – Effects Analysis (FMEA)

• Used to assess risks from potential product , service, transaction or process failure modes.

• Widely used in the Analyze and Improve phase, can also be used in Control phase.

• Helpful to assist in:– Improving or designing more robust products, services & processes– Designing safer products and processes– Designing safer delivery systems– Receiving fewer complaints and reducing the organization’s

guarantee costs– Creating fewer problems or minimizing them in everyday business

processes– Provide improvement teams with prioritized causes and identifying

which causes need to be eliminated urgently.

How does FMEA work?

• Focus on Severity, Occurrence and Detectability of each process. Then calculate the the Risk Priority number (RPN)• Each organization can define their own scale (1-10, 1-5… )as long as they are consistent across the organization.• Example of FMEA analysis for Auto manufacturer

– Start with a grid to define the potential failures

FMEASeverity, Occurrence & Detectability

SEVERITYSEVERITY

Product or Process

Failure Mode

Failure Effects

SEV Causes

OCC Controls

DET

RPN Actions

Engine OverheatEngine Damage 8

Radiator hose worn 5

Check frequently

Battery

Doesn't retain charge

Car doesn't start 8

Dry/dead battery 4

Service History

Brakes Brake failureCan't STOP car 10

worn brakepads 2

Replace worn pads


OCCURANCEOCCURANCE

Product or Process

Failure Mode

Failure Effects

SEV Causes

OCC Controls

DET

RPN Actions

Engine OverheatEngine Damage 8

Radiator hose worn 5

Check frequently 1 40

Replace Radiator Hose

Battery

Doesn't retain charge

Car doesn't start 8

Dry/dead battery 4

Service History 1 32 Change Battery

Brakes Brake failureCan't STOP car 10

worn brakepads 2

Replace worn pads 8 160

Revise Brakes frequently


PROBABILITY OF DETECTIONPROBABILITY OF DETECTION

• Risk Priority number (RPN) is calculated by multiplying

Severity x Occurrence x Detectabillity

Analytical Tool: XY Matrix

• XY matrix allows everyone involved with a process to agree on output (y’s) critical to the survey, transaction and/or customer.

• Matrix allows the team to assign the level of importance of each variable (x) to the output (y).

• EXAMPLE of XY matrix as relates to a coffee house.

• If the results/ranking were generated during a brainstorm session than they should be verified based on actual data.

OUTPUT VARIABLES (Y)Flavor Aroma Price Acidity RANK %RANK

Rankings 10 10 10 2

Coffee Type 10 10 10 10 320 24.4%Coffee Amount 9 7 10 10 280 21.4%Grind Time 9 6 2 3 176 13.4%Water Temp 9 3 2 2 144 11.0%Cup Type 2 4 4 2 104 7.9%Cup Size 2 4 5 1 112 8.5%Brew Time 9 6 2 2 174 13.3%

1310

INPU

T VA

RIAB

LES

(X)

Graphical Tool: Pareto Charts

• Pareto charts help identify the top factors (“vital few”)

• Order X in descending order.

• Add a line showing cumulative % of total.

• Based on this which inputs would you focus on to insure customer satisfaction?

Coffee Type

Coffee Amount

Grind Time

Brew Time

Water Temp Cup Size

Cup Type

Count 320 280 176 174 144 112 104

Percentage 24.4% 21.4% 13.4% 13.3% 11.0% 8.5% 7.9%

Cumulative % 24.4% 45.8% 59.2% 72.5% 83.5% 92.1% 100.0%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

0

200

400

600

800

1000

1200

1400

RAN

K

Coffee Pareto Chart

Graphical Tool: Histogram with Normal Curve

university-software.com/NormalHist.jpg

Graphical Tool: Histogram with Normal Curve

Minitab:Calc

Random DataInteger

StatBasic Statistics

Graphical Summary

Graphical Tool: Boxplot

Minitab:Stat

Basic StatisticsDisplay Descriptive..•Boxplot

• Minimum• Maximum• Median

• First Quartile• Third Quartile

Graphical Tool: Probability Plot

Minitab:Graph

Probability Plot•Single

Graphical Tool: Main-Effects Plot

• Main-effects plot graphically compares the level of a process output variable at various states of process factors

• Lines with steeper slopes have larger impact on the output compared to those lines with little or no slope

• Used to present result from analysis of variance (ANOVA)

• Use to examine the level means for each factor, compare the level means for several factors and compare the relative strength of the effects across factors

Graphical Tool: Main-Effects Plot

MINITABSTATANOVAMain Effect Plot

Input OutputX1 0 60 1 83X2 0 72

1 71X3 0 74 1 69

Graphical Tool: Run Chart

• A line graph of data points plotted in chronological order that helps detect special causes of variation– Understand process variation– Analyze data for patterns– Monitor process performance– Communicate process performance

Graphical Tool: Run Chart

www.pqsystems.com/.../chart_BasicRunChart.png

Graphical Tool: Time-Series Plot

• A time series plot is a graph showing a set of observations taken at different points in time and charted in a time series.– Outliers: values that do not appear to be consistent with

the rest of the data– Discontinuities: a break or gap in a process that would

normally be continuous– Trends: a general tendency in movement or direction– Periodicities: any recurrence at regular intervals

Graphical Tool: Time-Series Plot

cookbooks.opengrads.org/images/3/3b/Precip_ti..

Graphical Tool: Multi-Vari Charts

• Show patterns of variation from several possible causes on a single chart, or set of charts

• Obtains a first look at the process stability over time. Can be constructed in various ways to get the “best view”. – Positional: variation within a part or process– Cyclical: variation between consecutive parts or process steps– Temporal: Time variability


Cus. Size Product Cus. Type Satis.

1 1 2 3.54

2 1 3 3.16

1 2 2 2.42

2 2 2 2.70

1 1 3 3.31

2 1 2 4.12

2 2 1 3.24

2 2 2 4.47

2 1 2 3.83

1 1 1 2.94

Cus. Size: 1 = small2 = large

Product: 1 = Consumer2 = Manuf.

Cus. Type: 1 = Gov’t2 = Commercial3 = Education

http://www.qimacros.com/qiwizard/multivari-chart.html


Minitab:StatQuality ToolsMulti Vari Chart

Graphical Tool: Scatter Plot

• Show patterns of variation from several possible causes on a single chart, or set of charts

• Obtains a first look at the process stability over time. Can be constructed in various ways to get the “best view”. – Positional: variation within a part or process– Cyclical: variation between consecutive parts or process steps– Temporal: Time variability


http://mste.illinois.edu/courses/ci330ms/youtsey/scatterinfo.html







Graphical Tools for Process Rep.:Process Flowcharts

• Visual representation of the major process steps.• Useful to compare “as is” with “should be” process.

1. Determine the limits of the process. Clearly define where it begins & ends. 2. Determine the steps in the process3. Put the steps into sequence4. Draw the flow using standard symbols. Add arrows to show flow direction.5. Verify the flow is complete. Is every feedback loop complete?

Standard symbols:

Graphical Tools for Process Rep.:

Process Flowcharts

www.breezetree.com/.../8D-process-flowchart.png

Graphical Tools for Process Rep.:Process Mapping

• Process mapping is a workflow diagram to bring forth a clearer understanding of a process or series of parallel processes

• Cross-Functional Mapping• “As-is” vs. “To-be”

Graphical Tools for Process Rep.:Process Mapping

www.oregon.gov/.../images/

iGrafx_Process_Map.JPG

Graphical Tools for Process Rep.: SIPOC Diagram

• Supplier-Input-Process-Output-Customer diagram.• A high-level picture of the process that depicts how the

given process is servicing the customer. • Useful to discover customer “pain points”• Identify key Y’s an X’s with project team.

Suppliers Inputs Process Outputs Customers

Machine manufacturerBean supplierFilter supplierCup supplier

Coffee beansWaterFilterCupBrewing machine

Insert simple flow-chart hereCoffeeEspresso

Repeat (daily)New


http://www.ptm-consulting.it/immagini/sipoc.jpg

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Graphical Tools for Process Rep.: IPO Diagram

• Input-Process-Output diagram is another visual rep. of a process activity. Based on the transfer equation y=f(x)

x1=Forecast x2=BuyerX3 =AVLx4=BOMx5=LTx6=Market Dollar Value

Noise Variables(N)

Process X’s

ProcessProgram Management

ProcessProgram Management

Y=Lack of materials supplies

SO

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Fixed Variables (C)


http://www.variancereduction.com/newsletters/images/9.6.16.jpg

Other Tools:Force-Field Analysis

• Force-Field Analysis was developed by Lewin (1951) and is widely used to inform decision-making, particularly in planning and implementing change management programs in organizations.

• It is a powerful method for gaining a comprehensive overview of the different forces acting on a potential policy issue, and for assessing their source and strength.

Force-Field

Analysis

Other Tools:Matrix Analysis

• Technique for finding new combinations of products or services. – List the attributes of the product, service or strategy– Draw up a table using these attributes as column

headings– Write down as many variations of the attribute as possible

within these columns. – Select one entry from each column. By mixing one item

from each column, you will create a new mixture of components. This is a new product, service or strategy.

– Finally, evaluate and improve that mixture to see if you can imagine a profitable market for it.

Other Tools:Matrix Analysis

http://www.mindtools.com/pages/article/newCT_03.htm

Other Tools:Checksheets

• A check sheet is a structured, prepared form for collecting and analyzing data– Decide what event or problem will be observed. Develop operational

definitions.– Decide when data will be collected and for how long.– Design the form. Set it up so that data can be recorded simply by

making check marks or Xs or similar symbols and so that data do not have to be recopied for analysis.

– Label all spaces on the form.– Test the check sheet for a short trial period to be sure it collects the

appropriate data and is easy to use.– Each time the targeted event or problem occurs, record data on the

check sheet.

Other Tools:Checksheets

http://www.asq.org/learn-about-quality/data-collection-analysis-tools/overview/check-sheet.html

Other Tools:Scorecards

• A balanced scorecard is a central list of numbers, which show each key part of an organization's success, such as financials, people, operations, suppliers, customers, and support systems.

• The numbers should measure not just important outcomes, but also the factors which influence, or drive, those outcomes.

Other Tools:Scorecards

www.jiscinfonet.ac.uk/.../scorecard

Other Tools:Affinity Diagram

• The affinity diagram organizes a large number of ideas into their natural relationships– Record each idea with a marking pen on a separate sticky

note or card. Randomly spread notes on a large work surface so all notes are visible to everyone.

– Look for ideas that seem to be related in some way. Place them side by side. Repeat until all notes are grouped.

– Participants can discuss the shape of the chart, any surprising patterns, and especially reasons for moving controversial notes. When ideas are grouped, select a heading for each group.

– Combine groups into “supergroups” if appropriate.

Other Tools:Affinity Diagram

http://www.asq.org/learn-about-quality/idea-

creation-tools/overview/affinity.html

Affinity Diagram

http://www.asq.org/learn-about-quality/idea-

creation-tools/overview/affinity.html

Documents

Chapter 7 Quality Tools. Which tool is best? Tools can serve as the backbone for virtually any type of quality improvement effort (Six Sigma, TQM, 8D)