Six Sigma Statistical Terms - IV

Six Sigma Statistical Terms
GAGE LINEARITY
A measure of gage accuracy variation when evaluated over the expected operating range.

GAGE REPEATABILITY
A measure of the variation observed when a single operator uses a gage to measure a group of randomly ordered (but identifiable) parts on a repetitive basis.

GAGE REPRODUCIBILITY
A measure of average variation observed between operations when multiple operators use the same gage to measure a group of randomly ordered (but identifiable) parts on a repetitive basis.

GAGE STABILITY
A measure of variation observed when a gage is used to measure the same master over an extended period of time.

GREEN BELT
Six Sigma role similar in function to Black Belt but length of training and project scope are reduced.

HISTOGRAM
Vertical display of a population distribution in terms of frequencies; a formal method of plotting a frequency distribution.

HOMOGENEITY OF VARIANCE
The variances of the data groups being contrasted are equal (as defined by a statistical test of significant difference).

HYPOTHESIS
When used as a statistical term, it is a theory proposed or postulated for comparing means and standard deviations of two or more data sets. A “null” hypothesis states that the data sets are from the same statistical population, while the “alternate” hypothesis states that the data sets are not from the same statistical population.

INDEPENDENT VARIABLE
A controlled variable; a variable whose value is independent of the value of another variable.

INSTABILITY
Unnaturally large fluctuations in a process input or output characteristic.

INTERACTION
The tendency of two or more variables to produce an effect in combination which neither variable would produce if acting alone.

INTERVAL
Numeric categories with equal units of measure but no absolute zero point, i.e., quality scale or index.

KEY NOISE PARAMETERS
Variables which are hard or Expensive to control.

KEY PROCESS INPUT
The vital few input variables, called “x’s”, (normally 2-6)

VARIABLES (KPIV’S)
That drives 80% of the observed variations in the process output characteristic (“y”). a.k.a Key Control Parameters

LINE CHARTS
Charts used to track the performance without relationship to process capability or control limits.