ASQ - Six Sigma Forum



RAM: Reliability/availability/maintainability (see individual entries).

Random cause: A cause of variation due to chance and not assignable to any factor.

Random measurement error (or precision): The result of a measurement minus the mean that would result from an infinite number of measurements of the same measurand carried out under repeatability conditions. (The Uncertainty of Measurements)

Random sampling: A commonly used sampling technique in which sample units are selected so that all combinations of n units under consideration have an equal chance of being selected as the sample.

Range (statistical): The measure of dispersion in a data set (the difference between the highest and lowest values).

Range chart (R chart): A control chart in which the subgroup range, R, is used to evaluate the stability of the variability within a process.

Reactive customer-driven quality (RCDQ): A state that is characterized by a supplier "reacting" to the quality expectations of a customer, rather than proactively anticipating customer needs and expectations.

Red bead experiment: An experiment developed by W. Edwards Deming to illustrate it is impossible to put employees in rank order of performance for the coming year based on their performance during the past year because performance differences must be attributed to the system, not to employees. Four thousand red and white beads in a jar, 20% red, and six people are needed for the experiment. The participants' goal is to produce white beads because the customer will not accept red beads. One person begins by stirring the beads and then, blindfolded, selects a sample of 50 beads. That person hands the jar to the next person, who repeats the process and so on. When everyone has his or her sample, the number of red beads for each is counted. The limits of variation between employees that can be attributed to the system are calculated. Everyone will fall within the calculated limits of variation that could arise from the system. The calculations will show that there is no evidence one person will be a better performer than another in the future. The experiment shows that it would be a waste of management's time to try to find out why, say, John produced four red beads and Jane produced 15; instead, management should improve the system, making it possible for everyone to produce more white beads.

Reengineering: A breakthrough approach involving the restructuring of an entire organization and its processes.

Registrar Accreditation Board (RAB): A board that evaluates the competency and reliability of registrars (organizations that assess and register companies to the appropriate ISO 9000 series standards and to the ISO 14000 environmental management standard). RAB provides ISO course provider accreditation. Formed in 1989, RAB is governed by a board of directors from industry, academia and quality management consulting firms and by a joint oversight board for those programs operated with the American National Standards Institute (see listing).

Registration: The act of including an organization, product, service or process in a compilation of those having the same or similar attributes.

Registration to standards: A process in which an accredited, independent third-party organization conducts an on-site audit of a company's operations against the requirements of the standard to which the company wants to be registered. Upon successful completion of the audit, the company receives a certificate indicating that it has met the standard requirements.

Regression: The relationship between the mean value of a random variable and the corresponding values of one or more independent variables.

Regression analysis: A statistical technique for determining the best mathematical expression describing the functional relationship between one response and one or more independent variables.

Rejection number: The smallest number of defectives (or defects) in the sample or samples under consideration that will require the rejection of the lot.

Reliability: The probability of a product's performing its intended function under stated conditions without failure for a given period of time.

Relative standard deviation w/formula: Standard deviation divided by the mean. Calculated with the following formula: RSD= _ s / x. Relative standard deviation is often expressed as a percentage or as parts per thousand: RSD = _100% * s / x or _1000ppt * s / x.

Repeatability ( s(subscript: r) ): The closeness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions of measurement. (uncertainty of measurements)

Reproducibility ( s(subscript: R) ): The closeness of the agreement between the results of measurements of the same measurand carried out under changed conditions of measurement. (uncertainty of measurements)

Requirements: The ability of an item to perform a required function under stated conditions for a stated period of time.

Response surface design: An experimental design from which:

  1. Each factor has three or more levels
  2. Estimates of underlying model coefficient have little or no confounding
  3. The design matrix has the properties of:
    1. Matrix rotatability or near rotatability
    2. orthogonality, or near orthogonality.
  4. The model is:
    1. Full quadratic in the variables, including curvature terms
    2. Linear in the coefficients. (Quality Council of Indiana)

Results: The effects that relate to what is obtained by an organization at the conclusion of a time period.

Reverse logistics: Reverse logistics is the process of planning, implementing, and controlling the flow of finished goods from the point-of-consumption to the point-of-origin for the purpose of recapturing value or proper disposal.

Right the first time: A term used to convey the concept that it is beneficial and more cost effective to take the necessary steps up front to ensure a product or service meets its requirements than to provide a product or service that will need rework or not meet customer needs. In other words, an organization should engage in defect prevention rather than defect detection.

Risk management: An organized, analytic process identifying what can go wrong, quantifying and assessing associated risks, and implementing the appropriate approach to prevent or handle each identified risk. (Quality Council of Indiana). -or- The practice of methodically identifying and evaluating the potential impact of risks on a project or a business and then implementing mitigation or response strategies.

Robustness: The condition of a product or process design that remains relatively stable, with a minimum of variation, even though factors that influence operations or usage, such as environment and wear, are constantly changing.

Rolled throughput yield (RTY): The probability of a unit of product passing through an entire process defect-free.

Romig, Harry G. (deceased): An Honorary Member and founder of ASQ who was most widely known for his contributions in sampling. At AT&T Bell Laboratories, Romig and Harold F. Dodge developed the Dodge-Romig sampling tables, operating characteristics for sampling plans and other fundamentals. Romig alone developed the first sampling plans using variables data and the concept of average outgoing quality limit. Later in his life, Romig was a consultant and taught quality related courses at several universities.

Root cause: A factor that caused a nonconformance and should be permanently eliminated through process improvement.

Root-cause analysis: Study of original reason for nonconformance with a process. When the root cause is removed or corrected, the nonconformance will be eliminated. (Steve Littleton)

Run chart: A chart showing a line connecting numerous data points collected from a process running over a period of time.

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