Plan and Manage Quality of Products and Deliverables
Quality không phải là "test at the end" — là built-in từ đầu. PM phải phân biệt Quality Planning, Quality Assurance, và Quality Control. "Quality = fit for purpose, not gold-plating."
📖 Quality Triad: Plan → Assure → Control
Quality Planning (Plan Quality Management): Define quality standards, metrics, and how quality will be measured. Output: Quality Management Plan.
Quality Assurance (QA): Audit of quality PROCESSES to ensure they are being followed correctly. Proactive, done during execution. Identifies process improvements.
Quality Control (QC): Inspecting DELIVERABLES to verify they meet quality standards. Reactive, identifies defects. Compare to acceptance criteria.
Key distinction: QA = process audit (are we doing things right?). QC = product inspection (did we do it right?).
Gold-plating: Adding features beyond agreed scope "as a bonus." This is NOT quality improvement — it risks unintended impacts, wastes budget, and should be avoided.
Reference: PMI — Quality Management Fundamentals
Quality Planning: Xác định tiêu chuẩn chất lượng, metrics và cách đo lường. Output: Quality Management Plan.
Quality Assurance (QA): Kiểm tra QTRÌNH chất lượng để đảm bảo chúng đang được tuân thủ đúng. Proactive, thực hiện trong execution.
Quality Control (QC): Kiểm tra KẾT QUẢ để xác minh chúng đáp ứng tiêu chuẩn. Reactive, xác định defects.
Phân biệt quan trọng: QA = kiểm tra quy trình. QC = kiểm tra sản phẩm.
Gold-plating: Thêm tính năng ngoài phạm vi đã đồng ý "như một bonus" — KHÔNG phải cải thiện chất lượng, cần tránh.
| Aspect | Quality Assurance (QA) | Quality Control (QC) |
|---|---|---|
| Focus | Process (How we work) | Product/Deliverable (What we produce) |
| Timing | During execution (ongoing) | After work is done (inspection) |
| Nature | Proactive (prevent defects) | Reactive (find defects) |
| Who | PM, QA team, process auditors | QC team, testers, inspectors |
| Output | Process improvement recommendations | Verified deliverables, defect reports |
| Example | Auditing code review process compliance | Running regression tests on released build |
💰 Cost of Quality (CoQ)
Cost of Quality is the total cost incurred to prevent poor quality plus the cost when quality fails. Two categories:
Cost of Conformance (doing quality right):
- Prevention costs: Training, process design, standards documentation — costs to prevent defects
- Appraisal costs: Testing, inspections, audits — costs to find defects before delivery
Cost of Non-Conformance (paying for failures):
- Internal failure costs: Rework, scrap — defects found before delivery
- External failure costs: Warranty claims, lost business, reputation damage — defects found after delivery
PMP principle: Prevention is cheaper than inspection. Inspection is cheaper than failure. "Pay now or pay more later."
Cost of Quality (CoQ) là tổng chi phí để ngăn ngừa chất lượng kém + chi phí khi chất lượng thất bại.
Cost of Conformance (làm đúng từ đầu):
- Prevention costs: Training, thiết kế quy trình — chi phí ngăn ngừa lỗi
- Appraisal costs: Testing, kiểm tra — chi phí tìm lỗi trước khi giao
Cost of Non-Conformance (trả giá cho thất bại):
- Internal failure: Làm lại, hủy — lỗi tìm thấy trước khi giao
- External failure: Claim bảo hành, mất kinh doanh — lỗi tìm thấy sau khi giao
- QA = process, QC = product — this distinction is always tested
- Gold-plating is WRONG — even if well-intentioned, it's scope creep disguised as quality
- Prevention > Inspection > Internal failure > External failure (cost order, cheapest to most expensive)
- In Agile: quality is built in via Definition of Done, automated testing, and continuous integration
- Fitness for use = meeting customer needs. Conformance to requirements = meeting specifications. Quality = both.
- Deming's Plan-Do-Check-Act (PDCA) cycle underlies quality management
🔧 Quality Tools
| Tool | Purpose | When to Use | Example |
|---|---|---|---|
| Cause-and-Effect (Fishbone/Ishikawa) | Root cause analysis | When a quality defect is found | API timeout root cause: 6M framework (Machine, Method, Material, Man, Measurement, Environment) |
| Pareto Chart | 80/20 rule — identify top causes | Prioritizing defect resolution | 80% of bugs come from 20% of modules → focus there |
| Control Chart | Monitor process stability over time | Ongoing process monitoring | API response time tracked; alert when outside upper/lower control limits |
| Histogram | Distribution of defects by category | Understanding defect patterns | Bugs by sprint, by component, by severity |
| Scatter Diagram | Correlation between two variables | Testing cause-effect relationship | Team size vs defect rate correlation |
| Checksheet | Structured data collection | Manual inspection, audit | Deployment checklist, code review checklist |
💼 Thực chiến / Scenario
FinTech Company X — Quality Incident & Root Cause
Situation: Sprint 7 production deploy của Project Alpha. Critical defect: loan application data from Partner Bank A showing incorrect interest rates due to a rounding error in the credit engine. 3 customer applications affected before caught.
QC finding: Unit tests for the calculation module did not cover edge cases for rates above 18%. Integration tests didn't include real bank rate schedules.
QA process audit (Fishbone analysis):
- Method: Definition of Done did not require interest rate edge case coverage
- Man: Developer who built module was new PH team member, unfamiliar with local rate regulations
- Measurement: No acceptance criteria for rate calculation accuracy in stories
Cost of Non-Conformance: $15,000 in rework + remediation. $5,000 regulatory notification cost. No external failure — caught before broader impact.
Corrective actions (QA improvements): DoD updated to require rate edge case coverage. Acceptance criteria template updated with mandatory precision requirements. Partner bank rate schedule added to test fixtures.
PMP lesson: Quality management is a system — one defect reveals a process gap. Fix the process, not just the bug.
✏️ Practice Questions
- A. Quality assurance in action
- B. Gold-plating, which should be avoided
- C. Scope management best practice
- D. Proactive risk mitigation
- A. Quality Control
- B. Quality Assurance
- C. Quality Planning
- D. Cost of Conformance
- A. Fix all 20 modules equally since all bugs matter
- B. Focus quality improvement efforts on those 3 modules first — Pareto principle (80/20 rule) means maximum impact from targeted effort
- C. Remove the 3 problematic modules from scope
- D. Assign more testers to the other 17 modules
🤖 AI Tools for PMs
AI helps PMs generate QA checklists, analyze defect patterns using Pareto logic, draft root cause analyses, and create quality reports that connect technical metrics to business impact.