There are a lot of terms that are specific to Lean and Six Sigma. If you are unsure about the meaning of a term, please feel free to check our Lean and Six Sigma Glossary for a definition. If you do not find the term you are looking for, please contact us. We would be happy to answer your questions, and we may add your term to the glossary in the future.

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A broad concept and/or discipline involving degree of excellence; a distinguished attribute or nature; conformance to specifications; measurable standards of comparison so that applications can be consistently directed toward business goals.

Quality assurance, or QA

Discipline (or department) of maintaining product or service conformance to customer specifications; primary tools are inspection and SPC.

Quality council

Leadership group guiding the implementation of quality or Six Sigma within an organization; establishes, reviews, and supports the progress of quality improvement teams.

Random sampling

Method that allows each item or person chosen to be measured is selected completely by chance.


Design or redesign of business; similar to Process Redesign, though in practice usually at a much larger scale or scope.


Measurement stability concept in which a single person gets the same results each time he/she measures and collects data; necessary to ensure data consistency and stability. See also Reproducibility.


Measurement stability concept in which different people get the same results when they measure and collect data using the same methods; necessary to ensure data consistency and stability. See also Repeatability.

Revision plans

A mechanism (process) for updating processes, procedures, and documentation.

Rework loop

Any instance in a process when the thing moving through the process has to be corrected by returning it to a previous step or person/organization in the process; adds time, costs, and potential for confusion and more defects. See also Non-Value-Adding Activities.

Rolled throughput yield or RTY

The cumulative calculation of defects through multiple steps in a process; total input units, less the number of errors in the first process step number of items “rolled through” that step; to get a percentage, take the number of items coming through the process correctly divided by the number of total units going into the process; repeat this for each step of the process to get an overall rolled-throughput percentage. See also Yield.

Run chart, or time plot

Measurement display tool showing variation in a factor over time; indicates trends, patterns, and instances of special causes of variation. see also Control Chart; Special Cause; Variation.