Six Sigma Glossary - V

Six Sigma Glossay
Stable Process
A process which i free of assignable causes, e.g., in statistical control.

Standard Deviation
A statistical index of variability which describes the spread.

Statistical Control
A quantitative condition which describes a process that is free of assignable/special causes of variation, e.g., variation in the central tendency and variance. Such a condition is most often evidenced on a control chart.

Statistical Process Control
The application of statistical methods and procedures relative to a process and a given set of standards.

Transaction Processes
For Six Sigma purposes, defined as any business process that contributes to customer satisfaction or impacts operating efficiency and which is designated by a vice president or by GE Corporate as a focus for process improvement. Such efforts will be led by the process owner, with teams being led by specially trained transaction project leaders and/or by certified Black Belts.

Transaction Project Leader
An individual designated to lead a transaction process improvement project. Transaction project leaders attend a four-day course in specific Six Sigma tools and tactics.

Upper Control Limit
A horizontal line on a control chart (usually dotted) which represents the upper limits of process capability.

Variable
A characteristic that may take on different values.

Variables Data
A numerical measurement made at the interval or ratio level; quantitative data, e.g..,ohms, voltage, diameter; subdivisions, of the measurement scale are conceptually meaningful, e.g.., 1.6478 volts.

Variation
Any quantifiable difference between individual measurements; such differences can be classified as being due to common causes (random) or special causes (assignable).

“Xs”
Designation in Six  Sigma terminology for those variables which are independent, root causes; as opposed to “Ys” which are dependent outputs of a process. Six Sigma focuses on measuring and improving Xs, to see subsequent improvement in Ys.

X & R Charts
A control chart which is a representation of process capability over time; displays the variability in the process average and range across time.

“Ys”
Designation in Six Sigma terminology for those variables which are dependent outputs of a process, as opposed to “Xs” which are independent root causes.6M’s - Man, Machines, Materials, Methods, Measurement, Mother Nature

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