A short explanation of some terms used with the
Salland Engineering Data ANalysis Application.
AIAG |
Automotive Industry Action Group |
ANOVA |
Analysis Of Variance, Gage R&R study method. |
Appraiser |
Specific part of a gage, in ATE test engineering normally
a tester interface (DIB) or a specific test system. |
ATE |
Automatic Test Equipment. |
AV |
Appraiser Variation (reproducibility) |
%AV |
Percentage of AV/TW |
Average |
The result of dividing the total or sum of a group of measurements
by the number of things measured. |
Alias |
|
Bias |
 The
difference between the observed average of measurements and the reference
value. See image for a graphical explanation |
CDF |
Cumulative Distribution Function |
CM |
Correction for the Mean, the common factor in each of the
sum of squares calculations of the error sources according to the ANOVA
method. |
Capability index (Cp and Cpk) |
The number that expresses the capability of a process or
machine. To find this index number, compare the process spread to the specification
spread and express it in terms of the standard deviation. The Cp index does
not take into account where the process is centered with respect to the
tolerance of the part. |
Cpk hi
Cpk lo |
Capability index with respect to the High limitCapability
index with respect to the Low limitThe lowest index will be Cpk (total) |
Control chart |
A special type or graph showing the results of periodic small
inspections over time, like a movie of the process. A control chart tells
when to correct or adjust a process and when to leave it alone. |
Control limits |
Boundaries on a control chart within which the pointas plotted
can vary without the need for correction or adjustment. Control limits are
based on past performance and show what can be expected from a process as
long as nothing changes. |
CSV file format |
Comma Separated Value. A file format, used for loading
measurement data into SEDana. The format is for example used as an import
and export format in Excel or Access. |
Data |
Variable data: measurements of a sampled part. Attribute
data: pass/fail test results of a sampled part. |
DIB |
Device Interface Board (tester interface, load board). |
DF |
Degree of Freedom. For statistical analysis the total number
of degrees of freedom is one less than the sample size. |
Drift |
See stability |
DUT |
Device Under Test |
EV |
Equipment Variation (repeatability) |
%EV |
Percentage of EV/TW |
F (ratio) |
A ratio used in ANOVA to compare the magnitude of two estimates
of the population variance to determine if the two estimates area approximately
equal. |
FT |
Final Test. |
Gage (or: Gauge) |
Any device used to obtain measurements, in the ATE case normally
a test system, e.g. Teradyne Catalyst, including a specific DIB. |
GR&R |
Gage (or: Gauge) Repeatability and Reproducibility. |
%R&R |
Percentage of R&R/TW |
Guard band |
Difference between QA and FT limits for a specific parameter. |
HTL |
Higher Test Limit, normally FT limit. |
HSL |
Higher Specification Limit, normally QA limit. |
Interaction |
Found in GR&R. Non-additively between appraiser and part.
Appraiser differences depend on the part being measured. |
LCLr |
(Range) Lower Control Limit (GR&R definition). |
Linearity |
The difference in the bias values through the expected operating
range of the gage. |
LSL |
Lower Specification Limit, normally QA limit. |
LTL |
Lower Test Limit, normally FT limit. |
Normal Distribution |
The Normal (or Gaussian) Distribution is the most used probability
distribution in statistics. The distribution is characterized by a single-peaked,
bell-shaped curve. The mean lies at the center of the distribution. Because
the distribution is symmetrical, the mean and median values are equal. The
shape of the distribution is given by the standard deviation.99% of observations
are expected to lie within -2.575 and +2.575 standard deviations. |
Measurements system |
The collection of operations, procedures, gages and other
equipment, SW and personnel used to assign a number of the characteristic
being measured; the complete process used to obtain measurements. |
MDI |
Multi Document Interface |
Mean |
Arithmetic average of a set of observations. |
Median |
Arithmetic center value of a set of observations. |
MS |
Mean Square |
MSC |
Measurement System Comparison |
Operator |
See ‘Appraiser’. |
Out-of-Control |
Condition describing a process from which not all special
causes of variation have been eliminated. |
Part |
DUT or UUT. |
PDF |
Probability Density Function |
PP |
Process Performance. |
PPF |
Percent Point Function |
PV |
Part Variation |
%PV |
Percentage of PV/TW |
QA or QC |
Quality Assurance or Quality Conformance. |
R&R |
Repeatability and Reproducibility. |
Repeatability |
 The
variation in measurements obtained with one measurement instrument when
used several times by an appraiser while measuring the identical characteristic
on the same part. |
Replication error |
Repeatability error. |
Reproducability |
Reproducability is the variation in the average of the measurements made
by different appraisers using the same measuring instrument when measuring
the identical characteristics on the same part. (By defining a measuring
instrument as an appraiser, this measurement instrument does not necessarily
have to be the same.) |
SEDana |
Salland Engineering Data ANalysis Application |
SPC |
Statistical Process Control. See
separate document for more explanation |
SS |
Sum of Squares |
Stability |
Stability (or drift) is the total variation in the measurements
obtained with a measurement system on the same master or parts when measuring
a single characteristic over an extended time period. |
Standard Deviation |
The positive square root of the variance. |
STDF file format |
Standard Test Data Format. A typical file format used for
storing measurement data generated by Automatic Tester Equipment. The format
is developed by Teradyne and is now commonly used as a standard for tester
data. Most of the testers from Credence, Agilent, LTX and others can generate
this format. |
STDF V3 format |
File format used with older testers. Developed and described
by Teradyne |
STDF V4 format |
File format used with newer tester. Developed and described
by Teradyne. |
SW / HW |
Software / Hardware. |
TAG |
Test Apllication Group |
Trend |
Monotonically increasing or decreasing tendency of a variable
to change. |
Trial |
For ATE: test result for each of the parameters from a single
program run. |
TV |
Total Variation |
%TV |
Percentage of TV/TW |
TW |
Tolerance Width (HSL-LSL). |
UCLr |
(Range) Upper Control Limit (GR&R definition). |
USL |
Upper Specification Limit, normally QA limit. |
UTL |
Upper Test Limit, normally FT limit. |
UUT |
Unit Under Test, same as ‘DUT’. |