The maximum number of defects or defectives allowable in a sampling lot for the lot to be acceptable.
In a continuing series of lots, a quality level that, for the purpose of sampling inspection, is the limit of a satisfactory process average.
nspection of a sample from a lot to decide whether to accept that lot. There are two types attributes sampling and variables sampling. In attributes sampling, the presence or absence of a characteristic is noted in each of the units inspected. In variables sampling, the numerical magnitude of a characteristic is measured and recorded for each inspected unit; this involves reference to a continuous scale of some kind.
A specific plan that indicates the sampling sizes and associated acceptance or nonacceptance criteria to be used. In attributes sampling, for example, there are single, double, multiple, sequential, chain and skip-lot sampling plans. In variables sampling, there are single, double and sequential sampling plans.
A professional, not-for-profit association that develops, promotes and applies quality-related information and technology for the private sector, government and academia. ASQ serves individual and organizational members in more than 140 countries.
Name of ASQ from 1946 through the middle of 1997, when the name was changed to ASQ.
Not-for-profit organization that provides a forum for the development and publication of voluntary consensus standards for materials, products, systems and services.
The on-site verification activity, such as inspection or examination, of a process or quality system to ensure compliance to requirements. An audit can apply to an entire organization or might be specific to a function, process or production step.
The expected average quality level of an outgoing product for a given value of incoming product quality.
The maximum average outgoing quality over all possible levels of incoming quality for a given acceptance sampling plan and disposal specification.
The beginning point, based on an evaluation of output over a period of time, used to determine the process parameters prior to any improvement effort; the basis against which change is measured.
Fundamental ideas and tools that define the quality of a product or service. These include fitness for use, histograms, process capability indexes, cause and effect diagrams, failure mode and effects analysis, and control charts.
The comparison of a measurement instrument or system of unverified accuracy to a measurement instrument or system of known accuracy to detect any variation from the required performance specification.
The total range of inherent variation in a stable process determined by using data from
In acceptance sampling, a plan in which the criteria for acceptance and rejection apply to the cumulative sampling results for the current lot and one or more immediately preceding lots.
A tool for ensuring all important steps or actions in an operation have been taken. Checklists contain items important or relevant to an issue or situation. Checklists are often confused with check sheets (see listing).
The listing of possible defects of a unit, classified according to their seriousness. Note Commonly used classifications class A, class B, class C, class D; or critical, major, minor and incidental; or critical, major and minor. Definitions of these classifications require careful preparation and tailoring to the product(s) being sampled to ensure accurate assignment of a defect to the proper classification. A separate acceptance sampling plan is generally applied to each class of defects.
The state of an organization that meets prescribed specifications, contract terms, regulations or standards.
An affirmative indication or judgment that a product or service has met the requirements of a relevant specification, contract or regulation.
The external customer to whom a product or service is ultimately delivered; also called end user.
Pertains to sampling and the potential risk that bad products will be accepted and shipped to the consumer.
In acceptance sampling, a plan, intended for application to a continuous flow of individual units of product, that involves acceptance and rejection on a unit-by-unit basis and employs alternate periods of 100% inspection and sampling. The relative amount of 100% inspection depends on the quality of submitted product. Continuous sampling plans usually require that each t period of 100% inspection be continued until a specified number, i, of consecutively inspected units are found clear of defects.
Note: For single level continuous sampling plans, a single d sampling rate (for example, inspect one unit in five or one unit in 10) is used during sampling. For multilevel continuous sampling plans, two or more sampling rates can be used. The rate at any time depends on the quality of submitted product.
A time sequenced chart with upper and lower control limits on which values of some statistical measure for a series of samples or subgroups are plotted. The chart frequently shows a central line to help detect a trend of plotted values toward either control limit.
The natural boundaries of a process within specified confidence levels, expressed as the upper control limit (UCL) and the lower control limit (LCL).
Written descriptions of the systems for controlling part and process quality by addressing the key characteristics and engineering requirements.
A device that dimensionally measures 3-D products, tools and components with an accuracy approaching 0.0001 inches.
The system of rules, practices and processes that directs and controls an organization. In essence, corporate governance involves balancing the interests of an organization’s many stakeholders, such as shareholders, management, customers, suppliers, financiers, government and the community.
A solution meant to reduce or eliminate an identified problem.
A product’s or service’s nonfulfillment of an intended requirement or reasonable expectation for use, including safety considerations. There are four classes of defects class 1, very serious, leads directly to severe injury or catastrophic economic loss; class 2, serious, leads directly to significant injury or significant economic loss; class 3, major, is related to major problems with respect to intended normal or reasonably foreseeable use; and class 4, minor, is related to minor problems with respect to intended normal or reasonably foreseeable use. Also see “blemish,” “imperfection” and “nonconformity.”
A defective unit; a unit of product that contains one or more defects with respect to the quality characteristic(s) under consideration.
In numerical data sets, the difference or distance of an individual observation or data value from the center point (often the mean) of the set distribution.
The inability of an item, product or service to perform required functions on demand due to one or more defects.
A verification activity. For example, measuring, examining, testing and gauging one or more characteristics of a product or service and comparing the results with specified requirements to determine whether conformity is achieved for each characteristic.
Inspection of all the units in the lot or batch.
The cost associated with inspecting a product to ensure it meets the internal or external customer’s needs and requirements; an appraisal cost.
A collection of similar units or a specific quantity of similar material offered for inspection and acceptance at one time.
Inspection used in accordance with a sampling plan under ordinary circumstances.
Inspection in accordance with a sampling plan requiring smaller sample sizes than those used in normal inspection. Reduced inspection is used in some inspection systems as an economy measure when the level of submitted quality is sufficiently good and other stated conditions apply.
Note: The criteria for determining when quality is “sufficiently good” must be defined in objective terms for any given inspection system.
Inspection in accordance with a sampling plan that has stricter acceptance criteria than those used in normal inspection. Tightened inspection is used in some inspection systems as a protective measure when the level of submitted quality is sufficiently poor. The higher rate of rejections is expected to lead suppliers to improve the quality of submitted product.
Note: The criteria for determining when quality is “sufficiently poor” must be defined in objective terms for any given inspection system.
The complete measurement of all dimensions shown on a design record.
The total time a customer must wait to receive a product after placing an order.
A systematic method for waste elimination or minimization (muda) within a manufacturing system without sacrificing productivity.
The value of percentage defective or of defects per hundred units in a lot.
The number of units in a lot.
A top management meeting held at planned intervals to review the continuing suitability and effectiveness of one or more of an organization’s management system(s).
Methods, equipment and systems for conveying materials to various machines and processing areas, and for transferring finished parts to assembly, packaging and shipping areas.
A document for displaying the relationships among various data sets.
A measure of central tendency; the arithmetic average of all measurements in a data set.
All operations, procedures, devices and other equipment, personnel and environment used to assign a value to the characteristic being measured.
An organization’s purpose.
A particular way of accomplishing an expected outcome.
The method for ensuring that a process meets specified requirements.
The obligation of an organization to make restitution for loss related to personal injury, property damage or other harm caused by its product or service.
The application of knowledge, skills, tools and techniques to a broad range of activities to meet the specified requirements of a particular project.
A subjective term for which each person or sector has its own definition. In technical usage, quality can have two meanings.
1) the characteristics of a product or service that bear on its ability to satisfy stated or implied needs.
2) a product or service free of deficiencies. According to Joseph Juran, quality means “fitness for use”; according to Philip Crosby, it means “conformance to requirements.”
Two terms that have many interpretations because of the multiple definitions for the words “assurance” and “control.” For example, “assurance” can mean the act of giving confidence, the state of being certain or the act of making certain; “control” can mean an evaluation to indicate needed corrective responses, the act of guiding or the state of a process in which the variability is attributable to a constant system of chance causes. (For a detailed discussion on the multiple definitions, see ANSI/ISO/ASQ A3534-2, Statistics—Vocabulary and Symbols—Statistical Quality Control.) One definition of quality assurance is all the planned and systematic activities implemented within the quality system that can be demonstrated to provide confidence that a product or service will fulfill requirements for quality. One definition for quality control is the operational techniques and activities used to fulfill requirements for quality. Often, however, “quality assurance” and “quality control” are used interchangeably, referring to the actions performed to ensure the quality of a product, service or process.
A systematic, independent process of gathering objective evidence to determine whether audit criteria are being met. Audits are based on a sample and are independent of the system, process or product being audited, unlike verification activities, which are part of a process.
A quality improvement or self-improvement study group composed of a small number of employees (10 or fewer) and their supervisor. Quality circles originated in Japan, where they are called quality control circles.
See “quality assurance/quality control.”
Managing activities and resources of an organization to achieve objectives and prevent non-conformances.
A formal system that documents the structure, processes, roles, responsibilities and procedures required to achieve effective quality management.
Documented information that provides the activities or methods to be taken to achieve objectives and meet specified requirements.
A documented statement of commitment or intent to be implemented to achieve quality.
A commonly used sampling technique in which sample units are selected so all combinations of n units under consideration have an equal chance of being selected as the sample.
The smallest number of defectives (or defects) in the sample or samples under consideration that will require rejection of the lot.
In acceptance sampling, one or more units of product (or a quantity of material) drawn from a lot for purposes of inspection to reach a decision regarding acceptance of the lot.
The number of units in a sample.
A control chart in which the subgroup standard deviation, s, is used to evaluate the stability of the variability within a process.
As commonly used in acceptance sampling theory, the process of selecting sample units so all units under consideration have the same probability of being selected.
Note: Equal probabilities are not necessary for random sampling; what is necessary is that the probability of selection be ascertainable. However, the stated properties of published sampling tables are based on the assumption of random sampling with equal probabilities. An acceptable method of random selection with equal probabilities is the use of a table of random numbers in a standard manner.
Sampling inspection in which the inspection of the first sample leads to a decision to accept a lot, reject it or take a second sample; the inspection of a second sample, when required, then leads to a decision to accept or reject the lot.
Sampling inspection in which the decision to accept or reject a lot is based on the inspection of one sample.
Tools that help organizations understand their processes to improve them. The tools are the cause and effect diagram, check sheet, control chart, flowchart, histogram, Pareto chart and scatter diagram (see individual entries).
One standard deviation in a normally distributed process.
A term generally used to indicate process capability in terms of process spread measured by standard deviations in a normally distributed process.
The problem-solving tools used to support Six Sigma and other process improvement efforts. This includes voice of the customer, value stream mapping, process mapping, capability analysis, Pareto charts, root cause analysis, failure mode and effects analysis, control plans, statistical process control, 5S, mistake proofing and design of experiments.
Privately owned corporations, partnerships or sole proprietorships that have fewer employees and less annual revenue than a regular-sized business or corporation. The definition of “small”—in terms of being able to apply for government support and qualify for preferential tax policy—varies by country and industry.
A document that states the requirements to which a given product or service must conform.
The metric, specification, gauge, statement, category, segment, grouping, behavior, event or physical product sample against which the outputs of a process are compared and declared acceptable or unacceptable. Also, documents that provide requirements, specifications, guidelines or characteristics that can be used to ensure that materials, products, processes and services are fit for their purpose.
A source of materials, service or information input provided to a process.
The series of suppliers to a given process.
The act of examining a process or questioning a selected sample of individuals to obtain data about a process, product or service.
The American Supplier Institute’s trademarked term for the quality engineering methodology developed by Genichi Taguchi. In this engineering approach to quality control, Taguchi calls for off-line quality control, on-line quality control and a system of experimental design to improve quality and reduce costs.
A type of document in the International Organization for Standardization portfolio of deliverables.
The maximum and minimum limit values a product can have and still meet customer requirements.
A system that integrates quality development, maintenance and improvement of the parts of an organization. It helps an organization economically manufacture its product and deliver its services.
A term first used to describe a management approach to quality improvement. Since then, TQM has taken on many meanings. Simply put, it is a management approach to long-term success through customer satisfaction. TQM is based on all members of an organization participating in improving processes, products, services and the culture in which they work. The methods for implementing this approach are found in the teachings of such quality leaders as Philip B. Crosby, W. Edwards Deming, Armand V. Feigenbaum, Kaoru Ishikawa and Joseph M. Juran.
The ability of a feedback instrument to measure what it was intended to measure; also, the degree to which inferences derived from measurements are meaningful.
Analyzing the value stream to identify value added and nonvalue added activities.
A change in data, characteristic or function caused by one of four factors special causes, common causes, tampering or structural variation (see individual entries).
The act of determining whether products and services conform to specific requirements.
Items between machines or equipment waiting to be processed.
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