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| Difference between QA and QC |
Before we understand the meaning of 'Quality Assurance' and 'Quality Control', we need to understand the meaning of 'Assurance' and 'Control'.
Assurance
Assurance stands for a promise, a belief, or confidence. It is like a positive declaration, a manual, a plan, or an agreement intended to give confidence. It represents the plan of action. e.g. Showcasing a driving license to a traffic inspector provides the confidence to the inspector that the driver can able to drive the car.
Control
Control stands for the activities to manufacture a product within the specified limits or sustain a process with the lowest possible variation. e.g. control over the steering of the car, brakes, clutch, and gear for the smooth run of the car. Similarly, we can consider 100% inspection, random inspection, verification, and validity testing are a few activities of control that help to maintain and sustain the quality of the product.
What is quality?
Quality is the ratio of performance to expectation.
So if Q=(P/E) where 'P' is performance, 'E' is the expectation and naturally 'Q' is quality.
It is expected that an organization shall deliver a maximum of 1% defective parts in every lot.
- Now if the organization delivers more than 1% defectives that means the organization's manufacturing process has some problem and the performance of the process is not expected, and therefore the quality of the process is below par.
- If the organization delivers exactly 1% defectives as expected then the customer perceived the quality of the process of the organization is at par i.e. performance is the same as expected.
- If the organization delivers less than 1% defectives then, in that case, the quality of the process of the organization is above par i.e. the performance is greater than expected.
Hence the Quality Assurance includes the plan of action to control the quality or the performance of the process.
Quality Control is the bunch of activities that can control the quality or the performance of the process actually.
Difference between QA and QC under different contexts.
Definitions of QA and QC as per ISO9001
QA: A part of quality management focused on providing confidence that quality requirements will be fulfilled. It relates to how a process is performed, or how a product is made.
QC: A part of quality management focused on fulfilling quality requirements. It is more the inspection aspect of quality management
Functional Definitions
QA: All the planned and systematic activities are implemented within the quality system that can be demonstrated to provide confidence that a product or service will fulfill requirements for quality such as product or process audit.
QC: Operational techniques and activities are used to fulfill requirements of quality while manufacturing a product such as inspection and testing of the product
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Evolution
QA: 1950s; The quality profession expanded to include the quality assurance and quality audit functions.
QC: 1920s; Following the industrial revolution and rise of mass production. It became important to define and control the quality of products in a better way.
Focus
QA: Focus on planning and documenting the processes to assure quality such as quality plans, inspection plans, and test plans.
QC: Focus on physical verification that the product conforms to these planned arrangements through inspection, measurement, and testing.
Key Activities
QA: Development of quality plan, development of inspection plan, development of SOPs, evaluation of the quality system through audits, preparation of documents for QMS, etc.
QC: Implementation of the quality plan, follow the inspection plan and SOPs, control the quality of product through inspection, and implementation of QMS as per the documentation, etc.
Objective
QA: Prioritize the customer requirements and translate them into technical requirements for product development with the help of the engineering team using quality function deployment.
QC: Inspect the technical requirements of a product or service and conform against the specifications to meet the customer requirements using measuring, examining, and testing one or more characteristics.
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What they do?
QA: Prevent the quality problems through planned and systematic activities including documentation, SOPs, control plan, inspection plan, quality plan, FMEA, etc.
QC: Achieve and maintain the quality of product, process, and service using activities and techniques including 100% inspection, measurements, gauge R&R, Attribute R&R, etc.
How they do?
QA: Establish a good quality system and assessment of its adequacy through conformance audit of the operating system also the review of the system itself using product audit, process audit, and system audit.
QC: Find and eliminate the causes of quality problems so that customer requirement is continually met and the tools used for this purpose include; Why-Why analysis, cause and effect diagram, What is-What is not, etc.
Defect Control
QA: Predict potential defects right from the product development and process design, categorize the defects like critical, major and minor and establish a quality system that could prevent the occurrence of the defects such as prototype testing, Failure Mode Effect Analysis (FMEA), etc.
QC: Identify the defects and defectives through in-process inspection, sorting of defective parts through 100% inspection, and implement the inspection plan to prevent the escape of defective parts such as final inspection as per AQL.
Performance Evaluation
QA: Evaluate the performance of the product against a system, standard, or specified requirements for customers. e.g. Evaluation of the performance of a tyre with a particular car.
QC: Ensure the job management, competence, and performance during the manufacturing of the product or service within the system to ensure it meets the quality plan as designed e.g. testing the performance of a tyre while manufacturing.
As a Quality Tool
QA: Way of management, it is a complete system including the control also to assure the quality of the product or service.
QC: It is a process itself and part of the QA, just measures and determines the quality level of the products or services.
Overview
QA: It is a process-centric and proactive approach. It is a staff function that uses the 7 new QC Tools. It prevents the defects with help of quality audits and quality tools.
QC: It is a product-centric and reactive approach. It is a line function that uses 7 basic tools for process improvement. It finds the defects by a walk of the process, testing, and inspection.
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