Cost of quality analysis
Learning outcome statements
The learning outcome statements relevant for this section are:
- identify and describe the components of the costs of quality, commonly referred to as prevention costs, appraisal costs, internal failure costs, and external failure costs
- calculate the financial impact of implementing the above-mentioned processes
Introduction
COQ covers both the cost of achieving quality (prevention and appraisal spending) and the cost of failing to achieve it (internal and external failure costs). The rest of this section breaks down the four categories of quality costs and shows how shifting spending toward prevention and appraisal can lower the total cost of quality.
Categories of the costs of quality
The Costs of Quality (COQ) framework breaks down all quality-related expenditures into four main categories. These categories help organizations understand where their quality dollars are going and how to shift resources to maximize quality while minimizing total cost.
The four categories of quality costs can be broadly grouped into two overarching types:
Costs of good quality (conformance costs): prevention and appraisal costs. These include proactive investments made to ensure that products or services meet quality standards. Though they require upfront spending, these costs help minimize more serious and expensive issues downstream.
Costs of poor quality (nonconformance costs): internal and external failure costs. These arise when products or services fail to meet quality requirements, leading to rework, waste, customer dissatisfaction, or legal liability.
By increasing investments in good quality (prevention and appraisal), organizations can significantly reduce the more damaging and costly effects of poor quality over time.
1. Prevention costs
These are the costs incurred to prevent defects before they occur. Prevention focuses on process design, training, and quality planning to ensure products and services are right the first time. Examples of prevention costs:
- Employee training in quality control techniques
- Quality improvement projects (e.g., Six Sigma initiatives)
- Supplier evaluation and selection
- Process audits and preventive maintenance
2. Appraisal costs
These costs are related to measuring, inspecting, and monitoring to detect defects before the product reaches the customer. Appraisal ensures quality compliance during production. Examples of appraisal costs:
- Incoming materials inspection
- In-process and final product testing
- Calibration of testing and measurement equipment
- Internal quality audits
3. Internal failure costs
These are the costs of defects found before the product or service is delivered to the customer. They include expenses for rework, scrap, and delays due to quality issues. Examples of internal failure costs:
- Reworking defective products
- Scrap or disposal of unusable materials
- Downtime due to quality-related stoppages
- Re-inspection after correction
4. External failure costs
These are the costs of defects discovered after the product or service has been delivered to the customer. These failures can result in reputational damage and customer dissatisfaction. Examples of external failure costs:
- Product returns and warranty claims
- Complaint handling and customer service related to defects
- Legal liability and product recalls
- Loss of future sales due to poor quality perception
| Category | Purpose | Example activities |
| Prevention costs | Avoid defects before they occur | Training, quality planning, supplier assessment |
| Appraisal costs | Detect defects before customer delivery | Inspections, product testing, audits |
| Internal failure costs | Fix defects before delivery | Rework, scrap, re-inspection |
| External failure costs | Address defects after delivery | Returns, warranties, customer complaints |
Example: Financial impact of a quality program
Before investing in quality improvement, a company reports the following annual costs of quality:
- Prevention: $20,000
- Appraisal: $40,000
- Internal failure: $120,000
- External failure: $220,000
- Total COQ: $400,000
The company then launches a quality program that adds $60,000 of prevention spending (training and supplier certification) and $10,000 of appraisal spending. As a result, internal failure costs drop to $70,000 and external failure costs drop to $90,000.
After the program:
- Prevention: $20,000 + $60,000 = $80,000
- Appraisal: $40,000 + $10,000 = $50,000
- Internal failure: $70,000
- External failure: $90,000
- Total COQ: $80,000 + $50,000 + $70,000 + $90,000 = $290,000
Net savings: $400,000 − $290,000 = $110,000
If annual sales are $2,000,000, COQ fell from of sales to of sales.
Answer: shifting spending toward prevention and appraisal cut total COQ by $110,000 - from 20% to 14.5% of sales.
Some external failure costs, such as lost future sales from dissatisfied customers, are opportunity costs that never appear in the accounting records - they have to be estimated separately from the figures above.