A-Z Popular New Quality Search »
Quality
 
Related Guides
Quality Assurance

How Defect Rate is Calculated

 , updated on
A defect rate is the percentage of output that fails to meet a quality target. Defect rates can be used to evaluate and control programs, projects, production, services and processes.

Calculation

A defect rate is calculated by testing output for non-compliances to a quality target. Quality is typically specified by functional and non-functional requirements. The following formula can be used to calculate defect rate.
defect rate = (defects / output tested) x 100
Defects is the number of items that failed quality tests. Output tested is the total number of tests conducted.

Production

A bicycle production line tests every unit for defects. In a week, 4000 bicycles are produced and 3 fail quality tests.
defect rate = (3 / 4000) × 100 = 0.075%
Product lines may calculate multiple defect rates based on different levels of testing. For example, all bicycles may undergo standard quality testing with a small percentage randomly selected for more detailed testing. This results in a standard defect rate and detailed defect rate.

Code

Software testing tests 500,000 lines of code and discovers 33 defects.
defect rate = (33/500000) × 100 = 0.0066%
Code defects are also commonly measured as defects per thousand lines of code. This can be calculated with the formula:
defects per thousand lines of code = defects / (lines of code /1000)
In the example above this results in a defects per thousand lines of code of:
defects per thousand lines of code = 33 / (500000 / 1000) = 0.066

Use Cases

Software testing tests 33 use cases and discovers 4 defects.
defect rate = (4/33) × 100 = 12.12%
It is common to calculate defect rate according to the number of user stories, use cases, requirements or function points that are tested.

Services

Services may be tested for quality control with sampling of service interactions. For example, a call center evaluates 400 calls in a week for customer service quality and finds that 4 calls fail to meet quality standards.
defect rate = (4/400) × 100 = 1%
Automated services can also be tested for quality control purposes. For example, a website is tested for speed and errors 1000 times a day with 3 defects detected.
defect rate = (3/1000) × 100 = 0.3%
Overview: Defect Rate
Type
Definition
The percentage of output that fails to meet a quality target.
Related Concepts

Quality

This is the complete list of articles we have written about quality.
Benchmarking
Branding
Conformance Quality
Cost Of Poor Quality
Credence Quality
Critical To Customer
Critical To Quality
Customer Satisfaction
Data Quality
Defect Density
Defect Rate
Defensive Design
Design Quality
Document Quality
Durability
Ease Of Use
Experience Quality
Figure Of Merit
Fit For Purpose
Imperfection
Information Quality
Non-Functional Testing
Operational Testing
Perceived Value
Planned Obsolescence
Pokayoke
Product Quality
Quality
Quality Assurance
Quality Control
Quality Culture
Quality Examples
Quality Improvement
Quality Management
Quality Metrics
Quality Objectives
Quality Of Life
Quality Policy
Quality Requirements
Quality Testing
Recovery Paradox
Regression Testing
Reliability
Reliability Engineering
Resilience
Reusability
Service Quality
Types of Quality
Usability
Acceptance Testing
Work Quality
If you enjoyed this page, please consider bookmarking Simplicable.
 

Quality Control

A list of quality control techniques.

Quality Assurance vs Quality Control

The difference between quality assurance and quality control.

Quality Control Definition

Definitions of quality control.

Testing vs Quality Control

The difference between testing and quality control.

Conformance

A definition of conformance with examples.

Quality Specifications

A definition of quality specification with examples.

Administration Examples

An overview of administration with examples.

Quality Assurance Process

An overview of the quality assurance process.

Quality Improvement

An overview of quality improvement with examples.

Quality Culture

An overview of quality culture with examples.

Quality Inspection

The definition of quality inspection with examples.

Quality Control Process

A basic quality control process with examples.

Quality Planning

An overview of quality planning with examples.

Quality Assurance

A few quality assurance techniques.

Quality Assurance Definition

Definitions of quality assurance.

Quality Assurance Examples

An overview of quality assurance with a few examples.

Continuous Improvement

A definition of continuous improvement with examples.

Quality Policy

A list of common elements of a quality policy.

Acceptance Criteria Examples

A definition of acceptance criteria with examples.

Ishikawa Diagrams

The definition of ishikawa diagram with examples.

Problem Analysis

Common problem analysis techniques.

Quality Goals

Examples of measurable quality goals.
The most popular articles on Simplicable in the past day.

New Articles

Recent posts or updates on Simplicable.
Site Map