SPC Glossary 

Your quick reference to statistical process control for manufacturing quality managment systems.

Quality Management System Glossary:
D, E, F, G


Collected facts. 

There are two basic kinds of numerical data: measured or variable data (such as 12 ounces, 10 miles, and 0.50 inches) and counted (or attribute) data (such as 112 defects).

Data Collection and Analysis 

The process to determine what data are to be collected, how the data are collected, and how the data are to be analyzed.

Data Collection and Analysis Tools

A set of tools that help with data collection and analysis. These tools include check sheets, spreadsheets, histograms, trend charts, and control charts.


A product’s or service’s nonfulfillment of an intended requirement or reasonable expectation for use, including safety considerations. There are four classes of defects: Class 1, very serious, leads directly to severe injury or catastrophic economic loss; Class 2, serious, leads directly to significant injury or significant economic loss; Class 3, major, is related to major problems with respect to intended normal or reasonably foreseeable use; and Class 4, minor, is related to minor problems with respect to intended normal or reasonably foreseeable use. Also see Blemish, Imperfection, and Nonconformity.


A unit of product that contains one or more quality characteristic defects.

Deming Cycle

Also known as the Plan-Do-Study-Act cycle, popularized by W. Edwards Deming.

Also see Plan-Do-Check-Act Cycle.


The difference or distance of an individual observation or data value from the center point (often the mean) of the set distribution.


A mathematical model that relates the value of a variable with the probability of the occurrence of that value in the population.


Also known as Six Sigma DMAIC.

Define, Measure, Analyze, Improve, and Control. A data-driven quality strategy for improving processes, and an integral part of a Six Sigma quality initiative.


EWMA Charts

Also known as EWMA Control Charts.

An Exponentially Weighted Moving Average control chart uses current and historical data to detect small changes in the process. Typically, the most recent data are given the most weight, and progressively smaller weights are given to older data.


F Distribution

The F distribution is the probability distribution associated with the F statistic.

F Statistic

An F statistic is a value you get when you run an Analysis of Variance (ANOVA) test or a regression analysis to find out whether the means between two populations are significantly different.


The inability of an item, product, or service to perform required functions on demand due to one or more defects.


See Characteristic.

First Pass Yield (FPY)

Also referred to as the quality rate.

The percentage of units that completes a process and meets quality guidelines without being scrapped, rerun, retested, returned, or diverted into an offline repair area. Calculated by dividing the units entering the process minus the defective units by the total number of units entering the process.

First Time Quality (FTQ)

Also known as First Time Quality Formula.

Calculation of the percentage of good parts at the beginning of a production run.

Fitness for Use

The degree to which a product or service meets the requirements for its intended use.

14 Points

W. Edwards Deming’s 14 management practices to help organizations increase their quality and productivity: 1) Create constancy of purpose for improving products and services; 2) Adopt the new philosophy; 3) Cease dependence on inspection to achieve quality; 4) End the practice of awarding business on price alone; instead, minimize total cost by working with a single supplier; 5) Improve constantly and forever every process for planning, production and service; 6) Institute training on the job; 7) Adopt and institute leadership; 8) Drive out fear; 9) Break down barriers between staff areas; 10) Eliminate slogans, exhortations, and targets for the workforce; 11) Eliminate numerical quotas for the workforce and numerical goals for management; 12) Remove barriers that rob people of pride of workmanship and eliminate the annual rating or merit system; 13) Institute a rigorous program of education and self-improvement for everyone; and 14) Put everybody in the organization to work to accomplish the transformation.

Frequency Distribution (Statistical)

A list, table, or graph that displays the frequency of various outcomes in a sample.


Gauge Repeatability and Reproducibility (R&R)

A gauge R&R indicates whether the inspectors are consistent in their measurements of the same part (repeatability) and whether the variation between inspectors is consistent (reproducibility). 
  • Repeatability—How much variability in the measurement system is caused by the measurement device.
  • Reproducibility—How much variability in the measurement system is caused by differences between operators.
  • Whether your measurement system variability is small compared with the process variability.
  • Whether your measurement system is capable of distinguishing between different parts.

Geometric Dimensioning and Tolerancing (GD&T)

A language of symbols and standards designed and used by engineers and manufacturers to describe a product and facilitate communication between entities working together to produce something.


State of a unit or product. Two parameters are possible: Go (conforms to specifications) and No-Go (does not conform to specifications).

Green Belt (GB)

See Six Sigma Green Belt.

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