Key Takeaways
- PDCA (Plan-Do-Check-Act) cycle, also called the Deming Cycle, is the foundation for continuous improvement in quality management
- The Seven Basic Quality Tools include: Cause-and-Effect Diagrams, Flowcharts, Check Sheets, Pareto Charts, Histograms, Control Charts, and Scatter Diagrams
- Quality Assurance focuses on preventing defects through process improvement, while Quality Control focuses on detecting defects in deliverables
- Quality Audits are structured, independent reviews to ensure compliance with policies, processes, and procedures
- Cost of Quality (COQ) includes prevention costs, appraisal costs, internal failure costs, and external failure costs
Last updated: January 2026
Quality Management
Quality management ensures that the project will satisfy the needs for which it was undertaken. It addresses both the quality of the project deliverables and the quality of the project management processes used to create them.
Quality Management Processes
| Process | Purpose | Focus |
|---|---|---|
| Plan Quality Management | Identify quality requirements and standards | Planning |
| Manage Quality | Translate quality plan into activities | Prevention (QA) |
| Control Quality | Monitor results to ensure quality standards are met | Detection (QC) |
Plan-Do-Check-Act (PDCA) Cycle
The PDCA Cycle, also known as the Deming Cycle or Shewhart Cycle, is the foundation for continuous improvement:
PDCA Components
| Phase | Activities | Purpose |
|---|---|---|
| Plan | Identify improvement opportunity, analyze process, develop improvement plan | Define the change |
| Do | Implement the plan on a small scale, collect data | Test the change |
| Check | Analyze results, compare to expectations, identify lessons learned | Study the results |
| Act | Standardize successful changes, identify next improvement | Implement or iterate |
PDCA Application
- Quality audits and inspections occur in the Check phase
- Corrective actions are implemented in the Act phase
- The cycle repeats continuously for ongoing improvement
- Forms the basis for quality management system standards like ISO 9001
Quality Assurance vs. Quality Control
Key Differences
| Aspect | Quality Assurance (QA) | Quality Control (QC) |
|---|---|---|
| Focus | Process | Product |
| Approach | Prevention | Detection |
| Timing | Throughout project | During/after production |
| Goal | Prevent defects | Find defects |
| Activities | Process audits, training | Testing, inspection |
Quality Assurance Activities
- Process improvement
- Quality audits
- Training and development
- Procedure development
- Quality planning
Quality Control Activities
- Testing and inspection
- Peer reviews
- Measurement and monitoring
- Defect identification
- Statistical analysis
The Seven Basic Quality Tools
The Seven Basic Quality Tools (7QC Tools) are fundamental techniques for analyzing and solving quality problems:
Tool Overview
| Tool | Purpose | When to Use |
|---|---|---|
| Cause-and-Effect Diagram | Identify root causes of a problem | Problem investigation |
| Flowchart | Visualize process steps and flow | Process analysis |
| Check Sheet | Collect data systematically | Data gathering |
| Pareto Chart | Prioritize problems by frequency | Focus improvement efforts |
| Histogram | Show distribution of data | Understand variation |
| Control Chart | Monitor process stability | Track performance over time |
| Scatter Diagram | Show relationship between variables | Correlation analysis |
Cause-and-Effect Diagram
Also known as Ishikawa Diagram or Fishbone Diagram:
Structure
- Problem statement at the "head" of the fish
- Major cause categories form the "bones"
- Specific causes branch off from main bones
- Traces effects back to root causes
Common Categories (6 Ms)
- Manpower (People)
- Methods (Processes)
- Materials
- Machines (Equipment)
- Measurement
- Mother Nature (Environment)
Flowchart
Flowcharts display the sequence of steps in a process:
Elements
- Start/End (oval)
- Process step (rectangle)
- Decision point (diamond)
- Flow direction (arrows)
- Connectors (circle)
Benefits
- Visualize process flow
- Identify bottlenecks
- Find unnecessary steps
- Clarify handoffs
Check Sheet
A Check Sheet is a structured form for collecting and analyzing data:
Uses
- Count defect occurrences
- Track frequency by category
- Identify patterns
- Gather data for other tools
Example
| Defect Type | Mon | Tue | Wed | Thu | Fri | Total |
|---|---|---|---|---|---|---|
| Scratches | III | II | IIII | I | II | 12 |
| Dents | I | I | II | I | 5 | |
| Missing Parts | I | II | I | 4 |
Pareto Chart
Based on the Pareto Principle (80/20 rule): 80% of problems come from 20% of causes.
Components
- Bar chart showing frequency of causes (descending order)
- Cumulative line showing percentage
- Helps prioritize improvement efforts
Application
- Focus on the "vital few" causes
- Allocate resources effectively
- Track improvement over time
Histogram
A Histogram shows the distribution of numerical data:
Uses
- Understand data variation
- Identify patterns
- Detect outliers
- Compare to specifications
Interpretation
- Shape indicates process behavior
- Width shows variability
- Position shows central tendency
- Compare to tolerance limits
Control Chart
Control Charts monitor process stability over time:
Components
| Element | Description |
|---|---|
| Center Line (CL) | Process mean or target |
| Upper Control Limit (UCL) | +3 standard deviations |
| Lower Control Limit (LCL) | -3 standard deviations |
| Data Points | Individual measurements plotted over time |
Interpretation
| Pattern | Indication |
|---|---|
| Within limits, random | Process in control |
| Point outside limits | Special cause variation |
| 7+ points one side | Process shift |
| Trending pattern | Process drifting |
Control Limits vs. Specification Limits
| Limit Type | Set By | Purpose |
|---|---|---|
| Control Limits | Process data | What process IS doing |
| Specification Limits | Customer requirements | What process SHOULD do |
Scatter Diagram
Scatter Diagrams show the relationship between two variables:
Correlation Types
| Pattern | Correlation | Interpretation |
|---|---|---|
| Up slope | Positive | Variables move together |
| Down slope | Negative | Variables move opposite |
| No pattern | None | Variables unrelated |
Quality Audits
Quality Audits are structured, independent reviews:
Objectives
- Identify good practices and best practices
- Identify non-conformance and gaps
- Share best practices across the organization
- Proactively offer assistance to improve processes
- Confirm implementation of approved change requests
Types
| Type | Conducted By | Focus |
|---|---|---|
| Internal | Organization's own auditors | Compliance, improvement |
| External | Third-party auditors | Certification, compliance |
| Process | Quality team | Process effectiveness |
| Product | Quality team | Deliverable quality |
Cost of Quality (COQ)
Cost of Quality includes all costs incurred to prevent defects and fix problems:
Cost Categories
| Category | Type | Examples |
|---|---|---|
| Prevention Costs | Conformance | Training, planning, equipment maintenance |
| Appraisal Costs | Conformance | Testing, inspections, audits |
| Internal Failure Costs | Non-conformance | Rework, scrap, retesting |
| External Failure Costs | Non-conformance | Warranty, returns, liability |
COQ Principle
It is less expensive to prevent defects than to find and fix them.
Key Takeaways
- PDCA Cycle provides the framework for continuous improvement
- Quality Assurance prevents defects; Quality Control detects them
- The Seven Basic Quality Tools help analyze and solve quality problems
- Control Charts monitor process stability and distinguish common from special cause variation
- Quality Audits verify compliance and identify improvement opportunities
- Cost of Quality shows that prevention is cheaper than correction
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Test Your Knowledge
Which quality tool would be MOST appropriate to identify the root causes of recurring defects?
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B
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D
Test Your Knowledge
A control chart shows a data point above the Upper Control Limit. What does this indicate?
A
B
C
D
Test Your Knowledge
Which category of Cost of Quality represents the LEAST expensive approach to quality?
A
B
C
D