# Glossary “R” Definition of Terms in DataMyte

## R

Average range value displayed on a range control chart. Value is set when control limit(s) are calculated.

## R Chart

A control chart of the range of variation among the individual elements of a sample — i.e., the difference between the largest and smallest elements — as a function of time, or lot number, or similar chronological variable.

## Random

Varying with no discernable pattern.

## Random Sample

The process of selecting a sample of size n where each part in the lot or batch has an equal probability of being selected.

## Range

The difference between the highest and lowest of a group of values.

## Rational Subgrouping

For control charting: a subgroup of units selected to minimize the differences due to assignable causes. Usually samples taken consecutively from a process operating under the same conditions will meet this requirement.

## Regression Analysis

Provides the basis for predicting the values of a variable from the values of one or more other variables; correlation analysis enables us to assess the strength of the relationship (correlation) among the variables.

## Rejectable Quality Level (RQL)

For acceptance sampling: expressed as percentage or proportion of defective units; the poorest quality in an individual lot that should be accepted. Commonly associated with a small consumer’s risk. See also LTPD.

## Reliability

The probability that a product will function properly for some specified period of time, under specified conditions.

## Repeatability (of a measurement)

The extent to which repeated measurements of a particular object with a particular instrument produces the same value.

## Reproducibility

The variation between individual people taking the same measurement and using the same gauging.

## Resolution (of a measuring instrument)

The smallest unit of measure that an instrument is capable of indicating. See also Unit of Measure.

## Response Surface Methodology (RSM)

A method of determining the optimum operating conditions and parameters of a process by varying the process parameters and observing the results on the product. This is the same methodology used in Evolutionary Operations (EVOP), but is used in process development rather than actual production, so that strict adherence to product tolerances need not be maintained. An important aspect of RSM is to consider the relationships between the parameters, and the possibility of simultaneously varying two or more parameters to optimize the process.

## Route

For inspection, inventory, or other in-plant data collection: the sequence or path that the operator follows in the data collection process.

## Run

A set of consecutive units, e.g., sequential in time.