RAM (Reliability/Availability/Maintainability)

This term encompasses three key performance attributes:

• Reliability: The probability that a system or component performs its required function without failure for a specified period.
• Availability: The proportion of time a system is operable and accessible when needed.
• Maintainability: The ease and speed with which a system can be restored to operational status after a failure.
  See also: MTBF (Mean Time Between Failures), MTTR (Mean Time To Repair)

RACI Matrix

A responsibility assignment chart that outlines who is Responsible, Accountable, Consulted, and Informed for various tasks or decisions in a project. It clarifies roles and ensures that work is properly assigned and communicated.
See also: Role Clarification, Project Management

RACI (Responsible, Accountable, Consulted, Informed)

An acronym defining the four roles in a RACI matrix:

• Responsible: Those who do the work.
• Accountable: The person ultimately answerable for the correct completion.
• Consulted: Individuals whose opinions are sought.
• Informed: Those who are kept updated on progress.
  See also: RACI Matrix

RTY (Rolled Throughput Yield)

A Six Sigma metric that represents the compounded yield of a process over multiple steps. It is calculated by multiplying the yield of each process stage, indicating the probability that a unit is produced without defect through the entire process.
See also: Process Yield, Six Sigma Metrics

ROI (Return on Investment)

A financial metric that compares the net benefits (or savings) of an improvement or investment against its cost. It is used to evaluate the efficiency and profitability of an investment.
See also: Cost-Benefit Analysis, Investment Metrics

RPN (Risk Priority Number)

A score used in Failure Mode and Effects Analysis (FMEA) determined by multiplying ratings for Severity, Occurrence, and Detection. The RPN helps prioritize risks so that corrective actions can be effectively targeted.
See also: FMEA, Risk Assessment

RPN (Duplicate Entry)

Same as above—the Risk Priority Number identifies and prioritizes potential failure modes based on calculated risk.
See also: FMEA, Risk Management

Radar Chart

A graphical tool (also known as a spider or web chart) used to display multivariate data on a two-dimensional plane. Each axis represents a variable, and the plotted points are connected to form a polygon, making it easy to visualize performance across multiple dimensions.
See also: Data Visualization, Performance Dashboards

Random Cause

Also known as common cause variation, this term refers to the natural, inherent fluctuations observed in a process due to many small, unpredictable factors. These contrast with assignable causes, which are identifiable and correctable.
See also: Statistical Process Control (SPC), Process Variation

Random Sampling

A method of selecting a subset from a larger population in which every member has an equal chance of being chosen. This approach minimizes bias and increases the representativeness of the sample.
See also: Sampling Methods, Statistical Analysis

Randomized Block Design

A design of experiments technique that divides experimental units into homogeneous blocks. Treatments are randomly assigned within each block, reducing the impact of variability among blocks and increasing the reliability of results.
See also: Experimental Design, Analysis of Variance (ANOVA)

Range

A basic measure of statistical dispersion calculated as the difference between the maximum and minimum values in a dataset.
See also: Variance, Standard Deviation

Range Chart (R Chart)

A control chart used in Statistical Process Control (SPC) that monitors the variability within subgroups by plotting the range (difference between highest and lowest values) over time. It is particularly useful when sample sizes are small.
See also: Control Charts, Process Monitoring

Ranking

The process of ordering items, tasks, or issues based on specific criteria (such as performance, priority, or quality) to facilitate decision-making and prioritization.
See also: Prioritization, Decision Matrices

Rapid Improvement Event

Also known as a Kaizen Blitz, this is an intensive, short-term project where a cross-functional team focuses on identifying and quickly implementing process improvements. These events typically last from a few days to a week.
See also: Continuous Improvement, Lean Manufacturing

Regression Analysis

A statistical method used to examine the relationship between a dependent variable and one or more independent variables. It helps in forecasting, identifying trends, and establishing causal relationships.
See also: Predictive Analytics, Correlation Analysis

Regression Coefficient

A value obtained from regression analysis that quantifies the relationship between an independent variable and the dependent variable. It indicates the expected change in the dependent variable for a one-unit change in the independent variable, holding other factors constant.
See also: Linear Regression, Model Parameters

Regulatory Agency

An organization, typically governmental or quasi-governmental, that enforces laws and regulations within a specific industry to ensure safety, quality, and compliance. Examples include agencies like the FDA, EPA, or FCC.
See also: Compliance, Standards Organizations

Reengineering

Often referred to as business process reengineering, this involves the radical redesign of core business processes to achieve dramatic improvements in productivity, efficiency, and quality.
See also: Process Redesign, Innovation Strategy

Repetitiveness (Process Consistency)

The extent to which a process is performed in the same manner every time, leading to consistent outcomes. High repetitiveness often indicates a stable, controlled process with minimal variation.
See also: Standardization, Process Reliability

Replication (Experiment)

In the context of scientific experiments, replication refers to the repetition of an experimental procedure to confirm the reliability and validity of the results. It is essential for estimating experimental error and improving confidence in conclusions.
See also: Reproducibility, Experimental Design

Reproducibility

The ability to duplicate the outcomes of a study or experiment when it is replicated by different researchers under the same conditions. High reproducibility is a hallmark of reliable and credible research findings.
See also: Replication, Validation

Requirement

A specific, documented need or condition that a product, service, or process must satisfy. Requirements outline functional and performance parameters that help guide design, development, and validation efforts.
See also: Specification, User Needs

Requirements

The collective set of specifications and criteria that a system, project, or product must meet. This comprehensive list defines what is needed to meet stakeholder expectations and regulatory standards.
See also: Scope Definition, Requirement Engineering

Resolution (Design Resolution)

Refers to the level of detail and precision achieved in a design or measurement. In design, resolution can also denote how clearly a problem has been addressed or resolved.
See also: Design Detail, Problem Solving

Response Surface Methodology (RSM)

A collection of mathematical and statistical techniques used for modeling and analyzing problems in which a response of interest is influenced by several variables. RSM is used to optimize processes and improve performance by fitting a polynomial equation to experimental data.
See also: Design of Experiments (DoE), Process Optimization

Return on Investment (ROI)

(See previous ROI definition.) This metric assesses the profitability of an investment by comparing the net benefits to the investment’s cost. It serves as an indicator of financial efficiency and value.
See also: Investment Analysis, Cost-Benefit Analysis

Rework

Refers to the process of correcting or reprocessing defective items or errors in a product or service. Rework often results in additional labor and material costs and is used as an indicator of process inefficiency.
See also: Scrap, Process Improvement

Risk

The potential for an adverse event or variation that could impact objectives, including losses or missed opportunities. Risk is typically assessed based on probability and impact.
See also: Risk Assessment, Uncertainty Analysis

Risk Priority Number (RPN)

(See previous RPN definition.) Used in FMEA and other risk analysis methods, it quantifies risk by assigning numerical values to severity, occurrence, and detection, then multiplying them to prioritize issues.
See also: FMEA, Risk Management

Risk Analysis

The systematic process of identifying potential risks, evaluating their likelihood and impact, and determining their potential effects on objectives. It informs subsequent strategies to mitigate or manage risk.
See also: Risk Management, Hazard Analysis

Risk Management

A comprehensive approach to identifying, assessing, controlling, and monitoring risks that could affect an organization’s goals, projects, or processes. It involves proactive planning to mitigate adverse outcomes and capitalize on opportunities.
See also: Risk Analysis, Risk Assessment

Risk Assessment

The process of quantitatively or qualitatively evaluating risks to determine their probability and impact. It is a critical component of risk management that helps prioritize actions and allocate resources.
See also: Hazard Analysis, Risk Analysis

Robust Design

An engineering approach focused on designing products and processes that perform reliably under a wide range of conditions, minimizing the effects of variability and disturbances.
See also: Quality Engineering, Design for Six Sigma

Robustness

The quality of being able to maintain performance even in the presence of disturbances, variability, or changing operating conditions. A robust system delivers consistent results regardless of external factors.
See also: Robust Design, Process Stability

Rolled Throughput Yield (RTY)

(See RTY above.) This metric quantifies the overall efficiency of a process by calculating the probability that a unit passes through every sequential step defect-free.
See also: Process Yield, Six Sigma Metrics

Root Cause

The fundamental, underlying issue that leads to a problem or defect. Identifying the root cause is essential to developing effective and long-lasting solutions.
See also: Root Cause Analysis, Problem Solving

Root Cause Analysis (RCA)

A systematic method for investigating and identifying the underlying causes of a problem. RCA employs techniques such as the “5 Whys” or fishbone diagrams to drill down to the origin of issues in order to formulate corrective actions.
See also: Cause-and-Effect Analysis, 5 Whys

Run Chart

A simple line graph that plots data points in time sequence. Run charts are used to visualize trends, shifts, or patterns in process performance over time, aiding in performance monitoring and improvement initiatives.
See also: Control Charts, Process Monitoring