Transcript Sunny Fresh Foods

Chapter 11
Statistical
Thinking and
Applications
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
1
Key Idea
Raw data collected from the field do not
provide the information necessary for
quality control or improvement. Data must
be organized, analyzed, and interpreted.
Statistics provide an efficient and effective
way of obtaining meaningful information
from data, allowing managers and workers
to control and improve processes.
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
2
Statistical Thinking
• All work occurs in a system of interconnected
processes
• Variation exists in all processes
• Understanding and reducing variation are the
keys to success
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PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
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Sources of Variation in Production
Processes
Materials
INPUTS
Operators
Measurement
Instruments
Methods
PROCESS
OUTPUTS
Tools
Machines
Environment
MANAGING FOR QUALITY AND
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Thomson Higher Education Publishing
Human
Inspection
Performance
4
Variation
• Many sources of uncontrollable variation
exist (common causes)
• Special (assignable) causes of variation can be
recognized and controlled
• Failure to understand these differences can
increase variation in a system
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
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Key Idea
A system governed only by common
causes is called a stable system.
Understanding a stable system and the
differences between special and common
causes of variation is essential for
managing any system.
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
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Problems Created by Variation
•
•
•
•
•
Variation increases unpredictability.
Variation reduces capacity utilization.
Variation contributes to a “bullwhip” effect.
Variation makes it difficult to find root causes.
Variation makes it difficult to detect potential
problems early.
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
7
Importance of Understanding
Variation
time
PREDICTABLE
?
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
UNPREDECTIBLE
8
Two Fundamental Management
Mistakes
1. Treating as a special cause any fault, complaint,
mistake, breakdown, accident or shortage when
it actually is due to common causes
2. Attributing to common causes any fault,
complaint, mistake, breakdown, accident or
shortage when it actually is due to a special
cause
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
9
Note to Instructors
• The following slides can be used to guide a
class demonstration and discussion of the
Deming Red Bead experiment using small bags
of M&Ms, from a suggestion I found on a TQ
newsgroup several years ago. The good
output (“red beads”) are the blue M&Ms, with
the instructor playing the role of Dr. Deming.
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
10
We’re Going into Business!!!
We have a new global customer and have
to start up several factories. So I need
teams of 5 to do the work:
1 Production worker
2 Inspectors
1 Chief inspector
1 Recorder
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
11
Production Setup
1. Take the bag in your left hand.
2. Tear a 3/4” opening in the right
corner. (only large enough for one
piece at a time)
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
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Production Process
1. Production worker produces 10 pieces
and places them on the napkin.
2. Each inspector, independently, counts
the blue ones, and passes to the Chief
Inspector to verify.
3. If Chief Inspector agrees, s/he tells
the recorder, who reports it to me.
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
13
Do it right
the first
time!
Take Pride in
Your Work!
Be a Quality Worker!
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
14
Lessons Learned
• Quality is made at the top.
• Rigid procedures are not enough.
• People are not always the main source of
variability.
• Numerical goals are often meaningless.
• Inspection is expensive and does not
improve quality.
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
15
Statistical Foundations
•
•
•
•
•
•
Random variables
Probability distributions
Populations and samples
Point estimates
Sampling distributions
Standard error of the mean
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
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Important Probability Distributions
• Discrete
– Binomial
– Poisson
• Continuous
– Normal
– Exponential
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
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Central Limit Theorem
• If simple random samples of size n are taken from
any population, the probability distribution of
sample means will be approximately normal as n
becomes large.
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
18
Sampling Methods
•
•
•
•
•
Simple random sampling
Stratified sampling
Systematic sampling
Cluster sampling
Judgment sampling
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Key Idea
A good sampling plan should select a
sample at the lowest cost that will provide
the best possible representation of the
population, consistent with the objectives
of precision and reliability that have been
determined for the study.
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
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Sampling Error
• Sampling error (statistical error)
• Nonsampling error (systematic error)
• Factors to consider:
– Sample size
– Appropriate sample design
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PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
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Statistical Methods
• Descriptive statistics
• Statistical inference
• Predictive statistics
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
22
Statistical Tools
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
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Excel Tools for Statistics
• Tools…Data Analysis… Descriptive
Statistics
• Tools…Data Analysis…Histogram
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
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Key Idea
One of the biggest mistakes that people
make in using statistical methods is
confusing data that are sampled from a
static population (cross-sectional data)
with data sampled from a dynamic
process (time series data).
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Enumerative and Analytic Studies
• Enumerative study – analysis of a static
population
• Analytic study – analysis of a dynamic time
series
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Design of Experiments
• A designed experiment is a test or series of tests
that enables the experimenter to compare two or
more methods to determine which is better, or
determine levels of controllable factors to
optimize the yield of a process or minimize the
variability of a response variable.
• DOE is an increasingly important tool for Six
Sigma.
MANAGING FOR QUALITY AND
PERFORMANCE EXCELLENCE, 7e, © 2008
Thomson Higher Education Publishing
27