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Quality Glossary - R

R

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

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

Random sampling: 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.

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, evaluates the stability of the variability within a process.

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. Six people, 800 red beads and 3,200 white beads 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 in a jar and then, blindfolded, selecting 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 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 for restructuring an entire organization and its processes.

Registrar: Generally accepted U.S. equivalent term for “certification body.”

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 it has met the standard requirements. In countries outside the United States, this generally known as certification.

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 rejection of the lot.

Relations diagram: See interrelations diagram

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

Repeatability: The variation in measurements obtained when one measurement device is used several times by the same person to measure the same characteristic on the same product.

Reproducibility: The variation in measurements made by different people using the same measuring device to measure the same characteristic on the same product.

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

Resource utilization: Using a resource in a way that increases throughput.

Results: The effects that an organization obtains at the conclusion of a time period.

Right size: Matching tooling and equipment to the job and space requirements of lean production. Right sizing is a process that challenges the complexity of equipment by examining how equipment fits into an overall vision for workflow through a factory. When possible, right sizing favors smaller, dedicated machines rather than large, multipurpose batch processing ones.

Right the first time: 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: Using managerial resources to integrate risk identification, risk assessment, risk prioritization, development of risk handling strategies and mitigation of risk to acceptable levels.

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.

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

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

Runner: A person on the production floor who paces the entire value stream through the pickup and delivery of materials through kanban (see listing) usage.