Download 15.2 Single - Factor (One - Way) Analysis of Variance

Dimensions Of Product Quality (Garvin)
1. Core Performance
•basic operating characteristics
2. Features
•“extra” items added to basic features
3. Reliability
•probability product will operate, even in strenuous conditions
4. Convenience
•Amount of effort required to use the product
5. Durability
•life span before replacement
6. Serviceability
•ease of getting repairs, speed & competence of repairs
7. Aesthetics
•look, feel, sound, smell or taste
8. Safety
•freedom from injury or harm
9. Personal image
•subjective perceptions based on brand name, advertising, design
labels, etc
Additional Dimensions of Service Quality
1. Time & Timeliness
•customer waiting time, completed on time
2. Accessibility & Convenience
•ease of obtaining service
3. Face-to-Face interaction
•treatment by employees
4. Accuracy
•performed right every time
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The Meaning of Quality
Producer’s Perspective
Quality of Conformance
Production
•Conformance to
specifications
•Cost
Consumer’s Perspective
Quality of Design
•Performance quality
•Product’s bundle of
attributes & specifications
•Price
Fitness for
Consumer Use
Marketing
Quality Of Conformance
• Ensuring product or service produced according to design
• Depends on
•design of production process
•performance of machinery
•materials
•training
Two Ways Quality
Improves Profitability
Sales Gains via
 Improved response
 Flexible pricing
Improved
Quality
 Improved reputation
Reduced Costs via
 Lower rework and scrap costs
 Lower warranty & product
liability costs
Increased
Profits
Cost Of Quality
• Cost of achieving good quality
•Prevention
•Appraisal
• Cost of poor quality
•Internal failure costs
•External failure costs
Quality And Productivity
• Productivity = output / input
• Fewer defects increase output
• Quality improvement reduces inputs
Measuring Yield & Productivity
Y = (I)(%G) + (I)(1-%G)(%R)
where
Y = yield
I = number units started in production
% G = percentage good units
% R = percentage of defective units reworked
Product Yield Example
Start 100 motors per day
80% are good
50% of poor quality units can be reworked
Y = (I)(%G) + (I)(1-%G)(%R)
Y = 100 (0.80) + 100 (1- 0.80) (0.50) = 90 motors
Product Cost
direct mfg costinput  unit rework costreworked units

=
yield

K dI  K r R
=
Y
where
K d  direct manufacturing cost
I = input
Kr  rework cost per unit
R  reworked units
Y  yield
Product Cost Example
Direct mfg cost = $30, Rework cost = $12
100 motors started, 20% defective
50% of defective motors can be reworked

K dI  K r R
Product cost =
Y
$30100  $1210

=
 $34.67 per motor
90 motors
Total Quality Management
1. Customer defined quality and satisfaction
2. Top management leadership
3. Quality as a strategic issue
4. All employees responsible for quality
5. Continuous improvement
6. Shared problem solving/ Cross-discipline system
approach
7. Statistical quality control: measurement of results
8. Mutually beneficial supplier relations
Options to Improve Quality of Conformance
• Consumer Education: product labeling, instructions,
online resources
• Follow-up Service: Recalls, extended warranties,
replacements
• Inspection of Work and Product
• Preventative Procedures
Inspection
 Involves examining items to see if an item
is good or defective
 Detect a defective product
 Does not correct deficiencies in process or
product
 It is expensive
 Issues
 When to inspect
 Where in process to inspect
Inspection Tools
• System or process problems: Statistical process control
techniques
• Material or lot problems: Acceptance sampling techniques
Control Chart
10
UCL = 9.85
9
c = 6.17
Mg of salt
8
7
6
5
4
LCL = 2.99
3
2
4
6
8
10
12
Sample number
14
16
Preventative Procedures
• Improve Quality of Design: Design product/process for
robustness, poka-yoke, Taguchi Statistics
• Implement Six Sigma
• Involve Employees: Training, empowering, soliciting
input
• Form strategic supplier partnerships
• Remove safety nets: carrying JIT inventory and requiring
minimal lead times