Quality control

Quality control (QC) is a process by which entities review the quality of all factors involved in production. ISO 9000 defines quality control as "A part of quality management focused on fulfilling quality requirements".[1]

This approach places an emphasis on three aspects (enshrined in standards such as ISO 9001):[2][3]

  1. Elements such as controls, job management, defined and well managed processes,[4][5] performance and integrity criteria, and identification of records
  2. Competence, such as knowledge, skills, experience, and qualifications
  3. Soft elements, such as personnel, integrity, confidence, organizational culture, motivation, team spirit, and quality relationships.

Inspection is a major component of quality control, where physical product is examined visually (or the end results of a service are analyzed). Product inspectors will be provided with lists and descriptions of unacceptable product defects such as cracks or surface blemishes for example.[3]

The quality of the outputs is at risk if any of these three aspects is deficient in any way.

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Quality inspector in a Volkseigener Betrieb sewing machine parts factory in Dresden, East Germany, 1977.

History and introduction

Early stone tools such as anvils had no holes and were not designed as interchangeable parts. Mass production established processes for the creation of parts and system with identical dimensions and design, but these processes are not uniform and hence some customers were unsatisfied with the result. Quality control separates the act of testing products to uncover defects from the decision to allow or deny product release, which may be determined by fiscal constraints.[6] For contract work, particularly work awarded by government agencies, quality control issues are among the top reasons for not renewing a contract.[7]

The simplest form of quality control was a sketch of the desired item. If the sketch did not match the item, it was rejected, in a simple Go/no go procedure. However, manufacturers soon found it was difficult and costly to make parts be exactly like their depiction; hence around 1840 tolerance limits were introduced, wherein a design would function if its parts were measured to be within the limits. Quality was thus precisely defined using devices such as plug gauges and ring gauges. However, this did not address the problem of defective items; recycling or disposing of the waste adds to the cost of production, as does trying to reduce the defect rate. Various methods have been proposed to prioritize quality control issues and determine whether to leave them unaddressed or use quality assurance techniques to improve and stabilize production.[6]

Notable approaches

There is a tendency for individual consultants and organizations to name their own unique approaches to quality control—a few of these have ended up in widespread use:

Terminology Approximate year of first use Description
Statistical quality control (SQC) 1930s The application of statistical methods (specifically control charts and acceptance sampling) to quality control[8]:556
Total quality control (TQC) 1956 Popularized by Armand V. Feigenbaum in a Harvard Business Review article[9] and book of the same name.[10]; stresses involvement of departments in addition to production (e.g., accounting, design, finance, human resources, marketing, purchasing, sales)
Statistical process control (SPC) 1960s The use of control charts to monitor an individual industrial process and feed back performance to the operators responsible for that process; inspired by control systems
Company-wide quality control (CWQC) 1968 Japanese-style total quality control[10]
Total Quality Management (TQM) 1985 Quality movement originating in the United States Department of Defense that uses (in part) the techniques of statistical quality control to drive continuous organizational improvement[11]
Six Sigma (6σ) 1986 Statistical quality control applied to business strategy[12]; originated by Motorola
Lean Six Sigma (L6σ) 2001 Six Sigma applied with the principles of lean manufacturing and/or lean enterprise; originated by Wheat et al.[13]

In project management

In project management, quality control requires the project manager and/or the project team to inspect the accomplished work to ensure its alignment with the project scope.[14] In practice, projects typically have a dedicated quality control team which focuses on this area.[15]

See also


  1. ^ ISO 9000:2005, Clause 3.2.10
  2. ^ Praxiom Research Group Limited (16 August 2017). "ISO 9001 Translated Into Plain English". Praxiom Research Group Limited. Retrieved 29 November 2017.
  3. ^ a b Aft, L.S. (1997). "Chapter 1: Introduction". Fundamentals of Industrial Quality Control. CRC Press. pp. 1–17. |access-date= requires |url= (help)
  4. ^ Dennis Adsit (November 9, 2007). "What the Call Center Industry Can Learn from Manufacturing: Part I" (PDF). National Association of Call Centers. Retrieved 21 December 2012.
  5. ^ Dennis Adsit (November 23, 2007). "What the Call Center Industry Can Learn from Manufacturing: Part II" (PDF). National Association of Call Centers. Retrieved 21 December 2012.
  6. ^ a b Shewhart, Walter A. (Walter Andrew); Deming, W. Edwards (William Edwards) (1939). Statistical method from the viewpoint of quality control. Washington: The Graduate School, The Department of Agriculture. pp. 1–5.
  7. ^ "Position Classification Standard for Quality Assurance Series, GS-1910" (PDF). US Office of Personnel Management. March 1983. Retrieved 21 December 2012.
  8. ^ Juran, Joseph M., ed. (1995), A History of Managing for Quality: The Evolution, Trends, and Future Directions of Managing for Quality, Milwaukee, Wisconsin: The American Society for Quality Control, ISBN 9780873893411, OCLC 32394752
  9. ^ Feigenbaum, Armand V. (1956). "Total Quality Control". Harvard Business Review. Cambridge, Massachusetts: Harvard University Press. 34 (6): 93–101. ISSN 0017-8012. OCLC 1751795.
  10. ^ a b Ishikawa, Kaoru (1985), What Is Total Quality Control? The Japanese Way (1 ed.), Englewood Cliffs, New Jersey: Prentice-Hall, pp. 90–91, ISBN 978-0-13-952433-2, OCLC 11467749
  11. ^ Evans, James R.; Lindsay, William M. (1999), The Management and Control of Quality (4 ed.), Cincinnati, Ohio: South-Western College Publications, p. 118, ISBN 9780538882422, OCLC 38475486, The term total quality management, or TQM, has been commonly used to denote the system of managing for total quality. (The term TQM was actually developed within the Department of Defense. It has since been renamed Total Quality Leadership, since leadership outranks management in military thought.)
  12. ^ "What Is Six Sigma?" (PDF). http://www.motorolasolutions.com. Schaumburg, Illinois: Motorola University. 19 February 2010. p. 2. Archived from the original (PDF) on 3 December 2013. Retrieved 24 November 2013. When practiced as a management system, Six Sigma is a high performance system for executing business strategy. External link in |website= (help)
  13. ^ Wheat, B.; Mills, C.; Carnell, M. (2001). Leaning into Six Sigma: The Path to integration of Lean Enterprise and Six Sigma. Publishing Partners. p. 100. ISBN 9780971249103.CS1 maint: Multiple names: authors list (link)
  14. ^ Phillips, Joseph (November 2008). "Quality Control in Project Management". The Project Management Hut. Retrieved 21 December 2012.
  15. ^ Rose, K.H. (2014). Project Quality Management: Why, What and How. J. Ross Publishing. p. 224. ISBN 9781604271027.

Further reading

External links


A flowchart is a type of diagram that represents an algorithm, workflow or process. The flowchart shows the steps as boxes of various kinds, and their order by connecting the boxes with arrows. This diagrammatic representation illustrates a solution model to a given problem. Flowcharts are used in analyzing, designing, documenting or managing a process or program in various fields.

Food science

Food science is the science of nature devoted to the study of food; it is often confused with "food technology". The Institute of Food Technologists defines food science as "the discipline in which the engineering, biological, and physical sciences are used to study the nature of foods, the causes of deterioration, the principles underlying food processing, and the improvement of foods for the consuming public". The textbook Food Science defines food science in simpler terms as "the application of basic sciences and engineering to study the physical, chemical, and biochemical nature of foods and the principles of food processing".Activities of food technologists include the development of new food products, design of processes to produce these foods, choice of packaging materials, shelf-life studies, sensory evaluation of products using survey panels or potential consumers, as well as microbiological and chemical testing. Food scientists may study more fundamental phenomena that are directly linked to the production of food products and its properties.

Food science brings together multiple scientific disciplines. It incorporates concepts from fields such as chemistry, physics, physiology, microbiology, biochemistry... Food technology incorporates concepts from chemical engineering, for example.


A histogram is an accurate representation of the distribution of numerical data. It is an estimate of the probability distribution of a continuous variable (quantitative variable) and was first introduced by Karl Pearson. It differs from a bar graph, in the sense that a bar graph relates two variables, but a histogram relates only one. To construct a histogram, the first step is to "bin" (or "bucket") the range of values—that is, divide the entire range of values into a series of intervals—and then count how many values fall into each interval. The bins are usually specified as consecutive, non-overlapping intervals of a variable. The bins (intervals) must be adjacent, and are often (but are not required to be) of equal size.If the bins are of equal size, a rectangle is erected over the bin with height proportional to the frequency—the number of cases in each bin. A histogram may also be normalized to display "relative" frequencies. It then shows the proportion of cases that fall into each of several categories, with the sum of the heights equaling 1.

However, bins need not be of equal width; in that case, the erected rectangle is defined to have its area proportional to the frequency of cases in the bin. The vertical axis is then not the frequency but frequency density—the number of cases per unit of the variable on the horizontal axis. Examples of variable bin width are displayed on Census bureau data below.

As the adjacent bins leave no gaps, the rectangles of a histogram touch each other to indicate that the original variable is continuous.Histograms give a rough sense of the density of the underlying distribution of the data, and often for density estimation: estimating the probability density function of the underlying variable. The total area of a histogram used for probability density is always normalized to 1. If the length of the intervals on the x-axis are all 1, then a histogram is identical to a relative frequency plot.

A histogram can be thought of as a simplistic kernel density estimation, which uses a kernel to smooth frequencies over the bins. This yields a smoother probability density function, which will in general more accurately reflect distribution of the underlying variable. The density estimate could be plotted as an alternative to the histogram, and is usually drawn as a curve rather than a set of boxes. Histograms are nevertheless preferred in applications, when their statistical properties need to be modeled. The correlated variation of a kernel density estimate is very difficult to describe mathematically, while it is simple for a histogram where each bin varies independently.

An alternative to kernel density estimation is the average shifted histogram,

which is fast to compute and gives a smooth curve estimate of the density without using kernels.

The histogram is one of the seven basic tools of quality control.Histograms are sometimes confused with bar charts. A histogram is used for continuous data, where the bins represent ranges of data, while a bar chart is a plot of categorical variables. Some authors recommend that bar charts have gaps between the rectangles to clarify the distinction.

ISO/TS 16949

ISO/TS 16949 is an ISO technical specification aimed at the development of a quality management system that provides for continual improvement, emphasizing defect prevention and the reduction of variation and waste in the automotive industry supply chain. It is based on the ISO 9001 standard and the first edition was published in June 1999 as ISO/TS 16949:1999.It was prepared by the International Automotive Task Force (IATF) and the "Technical Committee" of ISO. It harmonizes the country-specific regulations of quality Management systems.About 30 percent of the more than 100 existing automobile manufacturers affiliate the requirements of the norm but especially the large Asian manufacturers have differentiated, own requirements for the quality management systems of their corporate group and their suppliers.ISO/TS 16949 applies to the design/development, production and, when relevant, installation and servicing of automotive-related products.

The requirements are intended to be applied throughout the supply chain. For the first time vehicle assembly plants will be encouraged to seek ISO/TS 16949 certification.


ISO 1 is an international standard set by the International Organization for Standardization that specifies the standard reference temperature for geometrical product specification and verification. The temperature is fixed at 20 °C, which is equal to 293.15 kelvin and 68 degrees Fahrenheit.Due to thermal expansion, precision length measurements need to be made at (or converted to) a defined temperature. ISO 1 helps in comparing measurements by defining such a reference temperature. The reference temperature of 20 °C was adopted by the CIPM on 15 April 1931, and became ISO recommendation number 1 in 1951. It soon replaced worldwide other reference temperatures for length measurements that manufacturers of precision equipment had used before, including 0 °C, 62 °F, and 25 °C. Among the reasons for choosing 20 °C was that this was a comfortable and practical workshop temperature and that it resulted in an integer value on both the Celsius and Fahrenheit scales.

Lil Baby

Dominique Jones, (born December 3, 1994) known professionally as Lil Baby, is an American rapper from Atlanta, Georgia. He is best known for his songs "My Dawg", “Freestyle”, "Yes Indeed" and "Drip Too Hard", the latter two peaking at number 6 and 4 respectively on the Billboard Hot 100 chart.

Lil Yachty

Miles Parks McCollum (born August 23, 1997), known professionally as Lil Yachty, is an American rapper, singer and songwriter. Yachty first gained recognition in August 2015 for his singles "One Night" and "Minnesota" from his debut EP Summer Songs. He released his debut mixtape Lil Boat in March 2016. On June 10, 2016, Yachty announced that he had signed a joint venture record deal with Quality Control Music, Capitol Records, and Motown Records. His mixtapes Lil Boat and Summer Songs 2 were released in 2016 and his debut studio album, Teenage Emotions in 2017. His second studio album, Lil Boat 2 was released on March 9, 2018.


Migos is an American hip hop trio from Lawrenceville, Georgia, founded in 2008. They are composed of three rappers known by their stage names Quavo, Offset and Takeoff. They are managed by Coach K, the former manager of Atlanta-based rappers Gucci Mane and Young Jeezy, and frequently collaborate with producers such as Zaytoven, DJ Durel, Murda Beatz, and Metro Boomin.Migos released their commercial debut single "Versace" in 2013, taken from their mixtape Y.R.N. (Young Rich Niggas). They have gone on to release several more singles, including "Fight Night" (2014), "Look at My Dab" (2015), and their four Billboard Hot 100 top 10 entries "Bad and Boujee" (featuring Lil Uzi Vert) (2016), peaking at number one, "MotorSport" (with Nicki Minaj and Cardi B) (2017), peaking at six, "Stir Fry" (2017), peaking at eight, and "Walk It Talk It" (featuring Drake) (2018), peaking at ten.

Migos released their debut album Yung Rich Nation in July 2015, through Quality Control Music and 300 Entertainment. Their second album, Culture, was released in January 2017 also through both record labels, and debuted atop the US Billboard 200 chart. The group later signed a deal with Motown and Capitol Records in February 2017, and followed up the latter album with Culture II in January 2018, giving the group their second number one album in the United States.

National Ambient Air Quality Standards

The U.S. National Ambient Air Quality Standards (NAAQS, pronounced \'naks\) are standards for harmful pollutants. Established by the United States Environmental Protection Agency (EPA) under authority of the Clean Air Act (42 U.S.C. 7401 et seq.), NAAQS is applied for outdoor air throughout the country.

Offset (rapper)

Kiari Kendrell Cephus (born December 14, 1991), known professionally as Offset, is an American rapper from Lawrenceville, Georgia. He is a member of the hip hop and trap music trio Migos, alongside cousins Takeoff and Quavo.

Pareto chart

A Pareto chart, named after Vilfredo Pareto, is a type of chart that contains both bars and a line graph, where individual values are represented in descending order by bars, and the cumulative total is represented by the line.

The left vertical axis is the frequency of occurrence, but it can alternatively represent cost or another important unit of measure. The right vertical axis is the cumulative percentage of the total number of occurrences, total cost, or total of the particular unit of measure. Because the values are in decreasing order, the cumulative function is a concave function. To take the example below, in order to lower the amount of late arrivals by 78%, it is sufficient to solve the first three issues.

The purpose of the Pareto chart is to highlight the most important among a (typically large) set of factors. In quality control, it often represents the most common sources of defects, the highest occurring type of defect, or the most frequent reasons for customer complaints, and so on. Wilkinson (2006)

devised an algorithm for producing statistically based acceptance limits (similar to confidence intervals) for each bar in the Pareto chart.

These charts can be generated by simple spreadsheet programs, such as Apache OpenOffice/LibreOffice Calc and Microsoft Excel, visualization tools such as ThoughtSpot or Tableau Software, specialized statistical software tools, and online quality charts generators.

The Pareto chart is one of the seven basic tools of quality control.

Quality Control Music

Quality Control Music (also known as Quality Control, QC the Label or simply QC) is an Atlanta-based record label founded by Pierre "Pee" Thomas and Kevin "Coach K" Lee in 2013. Its productions were distributed through Universal Music Distribution until it was dismantled in 2015; the label's releases are now distributed through Motown and Caroline, subsidiaries of the Capitol Music Group. Tamika Howard is the general manager of the label. Simone Mitchell is also an executive of the label.

The label has many acts signed, including the Migos (Quavo, Offset, and Takeoff), City Girls, Lil Yachty and Lil Baby. The label also has Cardi B signed under a management deal, as well as Trippie Redd, signed to its management company, Solid Foundation.

Quality assurance

Quality assurance (QA) is a way of preventing mistakes and defects in manufactured products and avoiding problems when delivering products or services to customers; which ISO 9000 defines as "part of quality management focused on providing confidence that quality requirements will be fulfilled". This defect prevention in quality assurance differs subtly from defect detection and rejection in quality control, and has been referred to as a shift left as it focuses on quality earlier in the process i.e. to the left of a linear process diagram reading left to right.The terms "quality assurance" and "quality control" are often used interchangeably to refer to ways of ensuring the quality of a service or product. For instance, the term "assurance" is often used as follows: Implementation of inspection and structured testing as a measure of quality assurance in a television set software project at Philips Semiconductors is described. The term "control", however, is used to describe the fifth phase of the Define, Measure, Analyze, Improve, Control (DMAIC) model. DMAIC is a data-driven quality strategy used to improve processes.Quality assurance comprises administrative and procedural activities implemented in a quality system so that requirements and goals for a product, service or activity will be fulfilled. It is the systematic measurement, comparison with a standard, monitoring of processes and an associated feedback loop that confers error prevention. This can be contrasted with quality control, which is focused on process output.

Quality assurance includes two principles: "Fit for purpose" (the product should be suitable for the intended purpose); and "right first time" (mistakes should be eliminated). QA includes management of the quality of raw materials, assemblies, products and components, services related to production, and management, production and inspection processes. The two principles also manifest before the background of developing (engineering) a novel technical product: The task of engineering is to make it work once, while the task of quality assurance is to make it work all the time.Historically, defining what suitable product or service quality means has been a more difficult process, determined in many ways, from the subjective user-based approach that contains "the different weights that individuals normally attach to quality characteristics," to the value-based approach which finds consumers linking quality to price and making overall conclusions of quality based on such a relationship.


Quavious Keyate Marshall (born April 2, 1991), known professionally as Quavo, is an American rapper, singer, songwriter and record producer. He is best known as a member of the hip hop and trap music trio Migos. Quavo is related to his fellow Migos members, being Takeoff's uncle and Offset's cousin.Outside of Migos, Quavo has been featured on four singles which have peaked within the top 10 of the Billboard Hot 100, including DJ Khaled's "I'm the One". On October 11, 2018, he released his debut solo album, Quavo Huncho which peaked at number 2 on the Billboard Hot 200.

Run chart

A run chart, also known as a run-sequence plot is a graph that displays observed data in a time sequence. Often, the data displayed represent some aspect of the output or performance of a manufacturing or other business process. It is therefore a form of line chart.

Scatter plot

A scatter plot (also called a scatterplot, scatter graph, scatter chart, scattergram, or scatter diagram) is a type of plot or mathematical diagram using Cartesian coordinates to display values for typically two variables for a set of data. If the points are color-coded, one additional variable can be displayed.

The data are displayed as a collection of points, each having the value of one variable determining the position on the horizontal axis and the value of the other variable determining the position on the vertical axis.

Statistical process control

Statistical process control (SPC) is a method of quality control which employs statistical methods to monitor and control a process. This helps to ensure that the process operates efficiently, producing more specification-conforming products with less waste (rework or scrap). SPC can be applied to any process where the "conforming product" (product meeting specifications) output can be measured. Key tools used in SPC include run charts, control charts, a focus on continuous improvement, and the design of experiments. An example of a process where SPC is applied is manufacturing lines.

SPC must be practised in 2 phases: The first phase is the initial establishment of the process, and the second phase is the regular production use of the process. In the second phase, a decision of the period to be examined must be made, depending upon the change in 5M&E conditions (Man, Machine, Material, Method, Movement, Environment) and wear rate of parts used in the manufacturing process (machine parts, jigs, and fixtures).

An advantage of SPC over other methods of quality control, such as "inspection", is that it emphasizes early detection and prevention of problems, rather than the correction of problems after they have occurred.

In addition to reducing waste, SPC can lead to a reduction in the time required to produce the product. SPC makes it less likely the finished product will need to be reworked or scrapped.

Stefflon Don

Stephanie Victoria Allen (born 14 December 1991), better known by her stage name Stefflon Don, is a British rapper from Hackney, London. She is best known for her 2017 single "Hurtin' Me" featuring French Montana, which peaked at number 7 on the UK Singles Chart. In 2016, Stefflon Don released her debut mixtape Real Ting, followed by another mixtape, Secure, in 2018.

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