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Introduction to Quality Improvement Tools
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5
10
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Category
Freq
uenc
yWe are what we repeatedly do. We are what we repeatedly do.
Excellence, then, is not an act but Excellence, then, is not an act but
a habit.a habit.
ARISTOTLEARISTOTLE
Quality Improvement Tools At the end of this learning module the learner
will: Understand how QI tools can support valid
decision making during the Quality improvement process
Describe 6 common QI tools Understand the advantages of each tool
The Deming Cycle
Plan
DoStudy
Act
Quality Tools Pareto Chart
Histogram Process flow diagram Check sheet Scatter diagram Control chart Run Chart Cause and Effect Diagram
Pareto Principle Vilfredo Pareto (1848-1923) Italian economist
20% of the population has 80% of the wealth Juran used the term “vital few, trivial many”.
He noted that 20% of the quality problems caused 80% of the dollar loss.
7 Quality Tools7 Quality Tools
Pareto chart
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64 3
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LooseThreads
Stitchingflaws
Buttonproblems
Materialflaws
% C
om
pla
ints
Pareto Chart
Per
cent
fro
m e
ach
caus
e
Causes of poor qualityM
achi
ne c
alib
ratio
ns
Defec
tive
parts
Wro
ng d
imen
sions
Poor D
esig
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Ope
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r erro
rsDef
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ater
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Surfa
ce a
bras
ions
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70(64)
(13)(10)
(6)(3) (2) (2)
Pareto analysis uses an ordered histogram to highlight the major causes of quality problems.
Advantages of a Pareto Diagram Helps a team focus on causes that have
the greatest impact Displays the relative importance of
problems in a simple visual format Helps prevent “shifting the problem” where
the solution removes some causes but worsens others
Histogram
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Histograms are graphical frequency tables that visually capture and display the variation in a set of data.
Advanatages of Histogram Displays large amounts of data that are
difficult to interpret in tabular form Shows centering, variation, and shape Illustrates the underlying distribution of the
data Provides useful information for predicting
future performance Helps to answer the question “Is the
process capable of meeting requirements?
Flowcharts Flowcharts
Graphical description of how work is done. Used to describe processes that are to be
improved.
7 Quality Tools7 Quality Tools
Flow Diagrams
" Draw a flowchart for whatever you do. Until you do, you do not know what you are doing,you just have a job.”
-- Dr. W. Edwards Deming.
FlowchartA flowchart diagrams the steps in a process. Flowcharts help problem solvers better understand the process so they can highlight quality problems.
Flow Diagrams
Flow Diagrams
Advantages of Flowcharts Shows unexpected complexity, problem
areas, redundancy, unnecessary loops, and where simplification may be possible
Compares and contrasts actual versus ideal flow of a process
Allows a team to reach agreement on process steps and identify activities that may impact performance
Serves as a training tool
Process Chart Symbols
Operations
Inspection
Transportation
Delay
Storage
Check Sheet
Creates easy-to-understand data Builds, with each observation, a clearer
picture of the facts Forces agreement o the definition of each
condition or event of interest Makes patterns in the data become
obvious quickly xx xxxxxx x
Check Sheet
COMPONENTS REPLACED BY LABTIME PERIOD: 22 Feb to 27 Feb 1998REPAIR TECHNICIAN: Bob
TV SET MODEL 1013
Integrated Circuits ||||
Capacitors |||| |||| |||| |||| |||| ||
Resistors ||
Transformers ||||
CommandsCRT |
A check sheet is a fact-finding tool used to collect data about quality problems.
A typical check sheet tallies the number of defects by previously identified categories. The next step is to graph the defects per category in a histogram.
Cause and Effect Diagram
Enables a team to focus on the content of a problem, not on the history of the problem or differing personal interests of team members
Creates a snapshot of collective knowledge and consensus of a team; builds support for solutions
Focuses the team on causes, not symptoms
Effect
Cause
QualityProblem
Materials
EquipmentPeople
Procedures
Cause and Effect Skeleton or Fishbone
A cause-and-effect diagram, or fishbone diagram, is a chart showing the different categories of problem causes.
Fishbone Diagram
QualityProblem
MachinesMeasurement Human
ProcessEnvironment Materials
Faulty testing equipment
Incorrect specifications
Improper methods
Poor supervision
Lack of concentration
Inadequate training
Out of adjustment
Tooling problems
Old / worn
Defective from vendor
Not to specifications
Material-handling problems
Deficienciesin product design
Ineffective qualitymanagement
Poor process design
Inaccuratetemperature control
Dust and Dirt
Cause and effect diagrams Advantages
making the diagram is educational in itself diagram demonstrates knowledge of problem
solving team diagram results in active searches for causes diagram is a guide for data collection
Show the relationships between a problem and its possible causes.
Developed by Kaoru Ishikawa (1953) Also known as …
Fishbone diagrams Ishikawa diagrams
Advantages of Cause-and-Effect Diagrams
Scatter Diagram
Supplies the data to confirm a hypothesis that two variables are related
Provides both a visual and statistical means to test the strength of a relationship
Provides a good follow-up to cause and effect diagrams
* * ** * *
Scatter Diagram
.
Scatter diagrams and tightness of points plotted on the graph gives an indication of the strength of the relationship.
A cluster of points resembling a straight line indicates the strongest correlation between the variables. In this graph, there is a strong positive correlation between x and y.
Run Charts Run Charts (time series plot)
Examine the behavior of a variable over time. Basis for Control Charts
Run Chart
Monitors performance of one or more processes over time to detect trends, shifts, or cycles
Allows a team to compare performance before and after implementation of a solution to measure its impact
Focuses attention on truly vital changes in the process
* * * * *
* *
Control Chart
Focuses attention on detecting and monitoring process variation over time
Distinguishes special from common causes of variation
Serves as a tool for on-going control Provides a common language for
discussion process performance
* * * * *
* *
Control Chart
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Sample number
Num
ber
of d
efec
ts
UCL = 23.35
LCL = 1.99
c = 12.67
Process control involves monitoring a production process and charting the results on a control chart. If any of the points plotted falls outside the control limits, the process is out-of-control.
The Seven QC Tools
1. Flowcharts
2. Check sheets
3. Histograms
4. Cause-and-effect diagrams
5. Pareto diagrams
6. Scatter diagrams
7. Control charts