Unit 3: Quality management
Production & Operations Management notes · PTU syllabus (MBA 205-18)
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Unit summary
Quality is defined by the customer and built in by the process. This unit covers the quality characteristics of goods and services, Juran's quality trilogy, Deming's 14 principles, statistical process control, TQM and Six Sigma, acceptance sampling plans and control charts for variables and defectives.
After this unit you can
- Explain the quality characteristics of goods and services
- Explain Juran's trilogy and Deming's 14 principles
- Explain statistical process control, TQM and Six Sigma
- Apply acceptance sampling plans and control charts
PTU syllabus topics
- Quality characteristics of goods and services
- Juran's Quality Trilogy
- Deming's 14 principles
- statistical process control
- TQM and Six Sigma
- acceptance sampling — single/double/multiple sample plans
- control charts for variables and defectives
- 1Quality planning
Design processes to meet needs
- 2Quality control
Measure and correct during operation
- 3Quality improvement
Raise performance to new levels
Topic 1
Quality characteristics of goods and services
Quality is fitness for use (Juran) or conformance to requirements (Crosby).
Performance
Primary operating characteristics
Features
Extras that add appeal
Reliability
Consistency over time
Conformance
Meeting specifications
Durability
Useful life
Serviceability
Ease of repair
Aesthetics
Look and feel
Perceived quality
Reputation
- Service quality (SERVQUAL): reliability, assurance, tangibles, empathy and responsiveness (RATER).
Topic 2
Juran's quality trilogy
- 1. Quality planning: Identify customers and needs; design products and processes
- 2. Quality control: Measure performance, compare with goals, act on gaps
- 3. Quality improvement: Project-by-project reduction of chronic waste
- Juran also stressed the Pareto principle — the "vital few" causes produce most problems.
Topic 3
Deming's 14 principles
- Create constancy of purpose for improvement.
- Adopt the new philosophy of quality.
- Cease dependence on mass inspection; build quality in.
- End awarding business on price alone; work with single suppliers.
- Improve constantly the system of production and service.
- Institute training on the job.
- Institute leadership.
- Drive out fear.
- Break down barriers between departments.
- Eliminate slogans and exhortations.
- Eliminate numerical quotas and management by objective.
- Remove barriers to pride of workmanship.
- Institute education and self-improvement.
- Put everyone to work on the transformation.
Topic 4
Statistical process control
SPC uses statistical tools to monitor a process and separate common (chance) causes of variation from assignable (special) causes.
- Seven basic QC tools (Ishikawa): check sheet, histogram, Pareto chart, cause-and-effect (fishbone) diagram, scatter diagram, flow chart, control chart.
Topic 5
TQM and Six Sigma
- Total Quality Management (TQM): a company-wide approach to continuous quality improvement focused on customer satisfaction, involving everyone. Principles: customer focus, continuous improvement (Kaizen), employee involvement, process approach, fact-based decisions and supplier partnerships. Deming's PDCA cycle (plan-do-check-act) drives improvement.
- Six Sigma: a data-driven method to reduce variation and defects to 3.4 defects per million opportunities, using DMAIC — Define, Measure, Analyse, Improve, Control. Experts are certified as Green Belts and Black Belts.
Topic 6
Control charts for variables and defectives
x̄ chart
UCL = x̿ + A2 R̄; LCL = x̿ − A2 R̄
R chart
UCL = D4 R̄; LCL = D3 R̄
p chart
p̄ ± 3√(p̄(1 − p̄)/n)
np chart
n p̄ ± 3√(n p̄(1 − p̄))
c chart
c̄ ± 3√c̄
Example
Ten samples of size 5 give x̿ = 50 and R̄ = 4; with A2 = 0.577, x̄-chart limits are 50 ± 0.577 × 4 = 47.69 to 52.31.
- Variables charts (x̄ and R) track measurable characteristics; attribute charts (p, np for defectives; c for defects) track counts.
- A process is out of control if points fall outside limits or show runs, trends or cycles.
Topic 7
Acceptance sampling
Acceptance sampling inspects a sample from a lot to accept or reject the whole lot.
Single sampling
One sample of n; accept if defectives ≤ c
Simple; larger average sample
Double sampling
Second sample if the first is inconclusive
Smaller average sample
Multiple sampling
Several small samples in sequence
Smallest average sample, complex
- OC curve: probability of accepting lots of different quality. AQL (acceptable quality level) and LTPD (lot tolerance percent defective) define producer's risk (α) and consumer's risk (β).
Key terms
- Quality trilogy
- Juran's planning, control and improvement
- Assignable cause
- Identifiable source of variation in a process
- Six Sigma
- 3.4 defects per million opportunities
- AQL
- Quality level accepted most of the time
- Producer's risk
- Probability of rejecting a good lot
Quick revision
- Garvin's eight dimensions; SERVQUAL (RATER).
- Juran: planning, control, improvement; Pareto.
- Deming's 14 points; PDCA.
- SPC; seven QC tools; TQM; Six Sigma (DMAIC).
- Control charts (x̄, R, p, np, c); single, double, multiple sampling; OC curve.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.State Garvin's dimensions of quality.
- Q2.What is Juran's quality trilogy?
- Q3.List any four of Deming's 14 points.
- Q4.Distinguish chance and assignable causes.
- Q5.What is DMAIC?
- Q6.What is an OC curve?
Long-answer questions
- Q1.Explain the quality characteristics of goods and services.
- Q2.Discuss Deming's 14 principles and Juran's trilogy.
- Q3.Explain TQM and Six Sigma.
- Q4.Explain control charts for variables and attributes and acceptance sampling plans.
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