✅ Key Concepts: Cost of Quality (CoQ)
The Cost of Quality is a framework to understand where time, effort, and money are spent in relation to product quality — whether proactively to prevent defects or reactively to fix them.
The 4 Categories of CoQ:
| Type | Description | Example Activities |
|---|---|---|
| Defect Prevention Costs | Proactive costs to prevent defects | Training developers, early reviews, good communication |
| Appraisal Costs | Costs for evaluating product quality and detecting defects before release | Static code analysis, test execution |
| Internal Failure Costs | Costs to fix defects found before release | Rework, debugging, retesting, re-deployment |
| External Failure Costs | Costs to fix defects found after release by customer | Refunds, legal costs, SLA penalties, support hotfixes |
👉 Boehm’s View: Emphasizes that early prevention is cheaper than dealing with late failures.
Cost of Quality
├── Prevention Costs
│ ├── Training
│ ├── Early reviews
│ └── Team communication
├── Appraisal Costs
│ ├── Static testing
│ ├── Unit/System/Integration Testing
│ └── Inspections
├── Internal Failure Costs
│ ├── Debugging
│ ├── Rework
│ └── Retesting
└── External Failure Costs
├── Customer support
├── Legal liabilities
├── Reputational damage
└── Financial loss
🧩 Short Scenarios (K2)
1. During a sprint, your team spends time doing peer reviews of user stories and test cases.
What cost of quality category does this fall under?
A. Appraisal
B. Prevention
C. External Failure
D. Internal Failure
✅ Answer: B. Prevention
2. The system was released with a bug causing invoice generation to fail, resulting in refund claims.
Which CoQ category applies?
A. Appraisal
B. Prevention
C. External Failure
D. Internal Failure
✅ Answer: C. External Failure
3. After a round of automated functional tests, several bugs are fixed before deployment.
Which CoQ category fits this?
A. Internal Failure
B. Appraisal
C. External Failure
D. Prevention
✅ Answer: A. Internal Failure
🧩 Long Scenario-Based MCQs (K2)
4. A bank’s mobile app development project includes regular requirements walkthroughs, pair programming, and knowledge-sharing sessions among developers. What category does this investment fall under in the cost of quality model?
A. Appraisal costs
B. Internal failure costs
C. External failure costs
D. Defect prevention costs
✅ Answer: D. Defect prevention costs
5. After production release, a retail company’s website crashes due to a missed performance defect. The company compensates customers and hires external consultants to fix the defect. What type of quality cost is this?
A. Appraisal cost
B. Internal failure cost
C. External failure cost
D. Prevention cost
✅ Answer: C. External failure cost
Q1.
A QA team introduces test design techniques early in the requirement phase and provides training on effective bug reporting.
What is the CoQ category?
A. Appraisal
B. Prevention
C. Internal Failure
D. External Failure
✅ Answer: B. Prevention
Explanation: Early training and proactive design reduce defects.
Q2.
You discover a UI issue during a final regression test, leading to rework.
Which category?
A. Prevention
B. Appraisal
C. Internal Failure
D. External Failure
✅ Answer: C. Internal Failure
Explanation: Detected before release, hence internal.
Q3.
A fintech firm is fined due to a security flaw that leaked customer data post-release.
Which CoQ category applies?
A. Prevention
B. Appraisal
C. Internal Failure
D. External Failure
✅ Answer: D. External Failure
Q4.
Testers review test plans and business rules to ensure alignment with regulatory compliance before execution starts.
A. Appraisal
B. Prevention
C. Internal Failure
D. External Failure
✅ Answer: B. Prevention
Q5.
Automated nightly build testing identifies 3 regressions, all fixed before UAT.
Which category?
A. Appraisal
B. Internal Failure
C. External Failure
D. Prevention
✅ Answer: B. Internal Failure
Q6.
After customer complaints, the team issues a hotfix and updates documentation.
What category?
A. Prevention
B. Appraisal
C. External Failure
D. Internal Failure
✅ Answer: C. External Failure
Q7.
You’re using code quality tools (like SonarQube) to detect vulnerabilities.
Which category?
A. Appraisal
B. Internal Failure
C. External Failure
D. Prevention
✅ Answer: A. Appraisal
Q8.
A mobile app project includes security awareness training for the development team.
What is this an example of?
A. Internal Failure
B. Appraisal
C. Prevention
D. External Failure
✅ Answer: C. Prevention
Q9.
The test team uses exploratory testing to uncover hidden UI defects before delivery.
Which category?
A. Appraisal
B. Internal Failure
C. Prevention
D. External Failure
✅ Answer: A. Appraisal
Q10.
A customer lodges a lawsuit due to serious data mismanagement by the system after go-live.
What is the cost category?
A. Internal Failure
B. Prevention
C. Appraisal
D. External Failure
✅ Answer: D. External Failure
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