Quality improvement methods

There are a lot many methods to improve the quality. Quality improvements can be people, process, product or technology based. The following list covers some of the main quality improvement methods.

Statistical Process Control (SPC) 

Process can be controlled statistically if the measurable parameter associated with the process is monitored on a continuous basis. The monitoring and controlling can be easily digested if charts are used for plotting the data. One of the seven Quality Control tools, known as Control chart is mainly used for this purpose.


Walter A. Shewhart made a major step in the evolution towards quality management by creating a method for quality control for production, using statistical methods, first proposed in 1924. This set the foundation for his ongoing work on statistical quality control. W. Edwards Deming later applied statistical process control methods in the United States during World War II, thereby successfully improving quality in the manufacture of munitions and other strategically important products.

Many SPC techniques have been “rediscovered” by American firms in recent years, especially as a component of quality improvement initiatives like Six Sigma.

Quality Function Deployment (QFD)

Quality Function Deployment is the method used in product design to identify the priorities for customer desires and expectations (the voice of the customer [VOC]) and to transfer these priorities into the technical design of the product. The QFD process is often referred to as listening to the Voice of the Customer.

Yoji Akao is widely regarded as the father of QFD. Quality Function Deployment uses the “House of Quality” as a visual model. The House of Quality is a matrix that aligns the Customer Needs (Business Priorities), the Design Features (Technical Priorities), and the Customer Preferences.  

There are other sets of quality tools for QFD as listed below

  • Affinity diagrams.
  • Relations diagrams.
  • Hierarchy trees.
  • Matrices and tables.
  • Process Decision Program Diagrams (PDPC)
  • The Analytic Hierarchy Process (AHP)
  • Blueprinting


The Kaizen method of continuous incremental improvements is an originally Japanese management concept for incremental (gradual, continuous) change (improvement). Key elements of Kaizen are quality, effort, and participation of all employees, willingness to change, and communication. Kaizen methodology includes making changes and monitoring results, then adjusting. PDCA cycle may be considered for implementing kaizen activities. KAIZEN can be practiced with the help of seven quality tools.

The term was made famous by Masaaki Imai in his book, “Kaizen: The Key to Japan’s Competitive Success. “

Zero Defect Program

Zero Defects, pioneered by Philip Crosby, is a business practice which targets to reduce the number of defects and errors in a process and to do things right the first time. The ultimate aim will be to reduce the level of defects to zero. However, this may not be practically feasible and hence what it means is that everything possible will be done to eliminate the likelihood of errors or defects occurring. The concept of zero defects has lead to the creation and development of six sigma pioneered by Motorola and now adopted worldwide by many other organizations.

Six Sigma 

Six Sigma is a disciplined, data-driven approach and methodology for eliminating defects in any process. Six Sigma stands for Six Standard Deviations from mean to the nearest specification limit. To achieve Six Sigma, a process must not produce more than 3.4 defects per million opportunities. There are two Six Sigma methodologies for process improvement

  • DMAIC (define, measure, analyze, improve, control) : It is an improvement system for existing processes falling below specification and looking for incremental improvement.
  • DMADV (define, measure, analyze, design, verify) : It is an improvement system used to develop new processes or products at Six Sigma quality levels. It can also be employed if a current process requires more than just incremental improvement.

Bill Smith, is known as Father of Six Sigma.                   


One of the most widely used paradigms in quality management is the PDCA (Plan-Do-Check-Act) approach. Walter Shewhart discussed the concept of the continuous improvement cycle (Plan Do Check Act) in his book, “Statistical Method From the Viewpoint of Quality Control“. W. Edwards Deming Modified and popularized the Shewart cycle (PDCA) to what is now referred to as the Deming Cycle (Plan, Do, Study, Act). In Six Sigma programs, the PDCA cycle is called “Define, Measure, Analyze, Improve and Control” (DMAIC).

There are other problem solving techniques as mentioned below

  • Creative Problem Solving Process (CPS): a six stage process
  • Productive Thinking Model, 6 step problem solving technique

Quality circle

Quality Circle is a small group of 6 to 12 employees with similar interests that meet at periodical intervals to discuss problems or other matters related to the quality of outputs of a process and to the correction of problems and thus leading to the improvement of quality.

Quality circles were first established in Japan in 1962, and Kaoru Ishikawa has been credited with their creation.

There are different quality circle tools, namely:

  • The Ishikawa diagram – which shows hierarchies of causes contributing to a problem
  • The Pareto Chart – which analyses different causes by frequency to illustrate the vital cause

Design of experiments

DOE is used to determine the relationship between the different factors (Xs) affecting a process and the output of that process (Y). This method was first developed in the 1920s and 1930, by Sir Ronald A. Fisher, the renowned mathematician and geneticist. A series of structured tests are designed in which planned changes are made to the input variables of a process or system. The effects of these changes on a pre-defined output are then assessed.

Just In Time, Toyota Production System & Lean Manufacturing

Lean Manufacturing is a systematic approach in identifying and eliminating waste through continuous improvement by flowing the product at the demand of the customer. Lean Manufacturing started as the Toyota Production System (TPS). Toyota’s engineers looked to Henry Ford (inventor of the assembly line – Ford System), Taylor, and Dr. W. Edwards Deming.  Henry Ford initiated the “Design for Manufacture” concept. According to him, a manufacturer should learn what all is absolutely required for any product and eliminate the useless part completely. Ever since the concept, also called the assembly line, has been implemented, the focus of the Industrialists has changed to produce maximum results with least possible inventory. Based on these early beginnings, the techniques were refined, and improved in all areas in Japan as TPS. The TPS has two pillar concepts: Just-in-time (JIT) or “flow”, and “autonomation” (smart automation).

A set of techniques that identify and eliminate waste has evolved in Lean Manufacturing as listed below

  • Cellular Manufacturing
  • Pull Scheduling (Kanban)
  • Six Sigma/Total Quality Management
  • Rapid Setup
  • Team Development

Kansei Engineering

Kansei is a Japanese term which means psychological feeling or image of a product. Kansei engineering refers to the translation of consumers’ psychological feeling about a product into perceptual design elements, invented in the 1970s by Professor Mitsuo Nagamachi (Dean of Hiroshima International University). Kansei Engineering can “measure” the feelings and shows the relationship to certain product properties. In consequence, products can be designed to bring forward the intended feeling.

An example: Sports cars can be described with adjectives like sporty, powerful, and elegant. Kansei Engineering can illustrate to what extent product attributes (e.g. the suspension, the gear ratio and the engine power) have an influence on these impressions.


Total Quality Management is a management strategy aimed at institutionalizing quality in all organizational processes. TQM is composed of three paradigms:

  • Total: Involving the entire organization, supply chain, and/or product life cycle
  • Quality: With its usual definitions, with all its complexities
  • Management: The system of managing with steps like Plan, Organize, Control

The fathers of TQM are generally recognized to include, among many others, W. Edwards Deming, Joseph M. Juran, George Box, and Philip Crosby in the United States and Genichi Taguchi and Kaoru Ishikawa in Japan.


The theory of inventor’s problem solving was developed by a Soviet engineer and researcher Genrich Altshuller and his colleagues starting in 1946.

Business Process Reengineering  (BPR )

Business process reengineering, a management approach aiming at ‘clean slate’ improvements (i.e. ignoring existing practices).


Poka-yoke is a Japanese term for mistake-proofing. A poka-yoke device is any mechanism that either prevents a mistake from being committed or makes the mistake obvious at a glance. Shigeo Shingo was one of the industrial engineers at Toyota who has been credited with creating and formalizing Zero Quality Control (ZQC), an approach to quality management that relies heavily on the use of poka-yoke devices.

Failure Mode and Effects Analysis (FMEA)

FMEA is a procedure for analysis of potential failure modes within a system and determination of the effect of failures on the system. In FMEA, failures are prioritized according to how serious their consequences are, how frequently they occur and how easily they can be detected. The purpose of the FMEA is to take actions to eliminate or reduce failures, starting with the highest-priority ones. It may be used to evaluate risk management priorities.

Advance Product Quality Planning (APQP).

Advanced Product Quality Planning (APQP) is a quality framework used for developing new products in the automotive industry. It can be applied to any industry and is similar in many respects to the concept of design for six sigma (DFSS). The APQP process is described in AIAG manual 810-358-3003. Its purpose is “to produce a product quality plan which will support development of a product or service that will satisfy the customer.” It does this by focusing on:

  • Up-front quality planning
  • Evaluating the output to determine if customers are satisfied & support continual improvement

Hoshin Planning

Hoshin planning is a Japanese strategic planning process in which an organization develops up to four vision statements that indicate where the company should be in the next five years. Company goals and work plans are developed based on the vision statements. Periodic audits are then conducted to monitor progress.