Glossary Primary Words
1. Break
2. Break Set
3. Decay
4. Homogeneous
5. Hook-up Replicate
6. Lot
7. Lot Control Standard (LCS)
8. Lot Control Standard Set (LCS Set)
9. Local Drift
10. Noise
11. Outlier
12. Reproducibility
Break
A "break" is any interruption (coffee break, lunch break,
end of day, power outage, etc.) which disrupts the
physical flow of data during the chemical analysis
process.
Break Set
A "break set" is the set of chemical measurements
collected in the interim between 2 breaks; in particular:
1) all test cylinder readings collected up to the first break
would be considered to have come from "break set 1";
2) all test cylinder readings collected between the first
and second break would be considered to have come
from "break set 2"; and so forth.
Over them lifetime of the 3- or 4-day chemical analysis,
it is not uncommon to have 3 to 10 break sets.
With new instrumentation which is highly automated,
the number of breaks will be substantially reduced.
Decay
Decay in a cylinder refers to the decrease in the
true concentration of a cylinder over time (usually
months). Decay is an unavoidable fact-of-life for the
"unstable" gases such as SO2, NOX, H2S, etc.; decay is
less of a problem for most other gases
Decay is sometimes referred to as global drift, but such
designation is not recommended because "drift" is here
restricted to changes (increases/ decreases) in the
instrument response (as opposed to the true
concentration) due to non-cylinder factors such as
instrument, port, environemnt, day, etc.
Homogeneous
The lot of cylinders is said to be "homogeneous" if the
concentrations across all cylinders in the lot are not
significantly different from both a chemical and a
statistical point of view. When a lot is
homogenous, then the lot may be
batch (= globally) certified--that is a common gas concentration
value is determined and that common value is assigned to
all cylinders in the lot, with a common value for the
uncertainty on the true concentration.
If the lot is determined to be inhomogenous (= heterogeneous)
then either:
1. the cylinders are individually certified with
individual uncertainties (a time-intensive
alternative); or
2. the cylinders are batch (= globally) certified with
a common uncertainty; note, however that such
uncertainty will tend to be large because
prediction intervals will be used rather than
confidence intervals.
On the other hand, if the common uncertainty is still
small enough by chemical standards, then method 2 will be
used; else method 1 will be used.
Hook-up Replicate
Over the several days of the chemical analysis,
each test cylinder is usually manaually hooked up
to the measuring instrument at least once, and
sometimes 2 or 3 times. For a specific cylinder:
1) all of the readings that were taken on the cylinder
during the first hook-up would be considered to
have come from "hook-up replicate 1";
2) all of the readings collected on a specific
cylinder during the second hook-up would be
considered to have come from "hook-up replicate 2"; etc.
An implicit assumption is that there is no difference in
the measured concentrations between the hook-up replicates
for a given gas cylinder. This assumption should be
statistically checked and verified.
Local Drift (= Drift)
"Local drift" (or simply "drift") is the systematic,
non-random (structured, deterministic) short-term (up to
a few days) change in the measurement instrument response
due to instrument, environment, etc. Such deterministic
changes are commonly linear, quadratic, sinusoidal, etc.
Such changes are most easily detected by the use of lot
control standards.
Lot (= Batch)
A collection of gas cylinders is a "lot" or a "batch" if
they were fabricated together in a contiguous block of
time, and delivered together as a lot to be certifed.
Typical lot sizes are 50 to 100 cylinders.
Ideally a lot is homogenous, so that global
certification of the lot will suffice. Testing for
homogeneity within a lot is a critical element in the
statistical analysis.
Lot Control Standard (= Lot Control Standard = LCS)
This is a representative cylinder (sometimes larger in
size) chosen from the lot of cylinders to be certified.
The purpose of the lot control standard is to detect,
assess, and correct time drift. When drift is detected,
the test cylinder readings are corrected according the
behavior of the readings of the LCS.
Lot Control Standard Set (LCS Set)
For drift assessment/correction reasons, the chemical
analysis experiment design ideally intersperces test
cylinder readings with readings from a designated
standard cylinder (the LCS: the lot control standard).
1) After an initial LCS reading is taken, all test cylinder
readings up to (but excluding) the second LCS reading
would be considered to have come from "LCS set 1";
2) all test cylinder readings collected between the second
and third LCS readings would be considered to have come
from "LCS set 2", and so forth.
Over the lifetime of the 3-or 4-day chemical analysis,
it is not uncommon to have a large number (e.g., 30 or
40) LCS sets. In the presence of drift, all test
cylinders within a LCS set will have common corrections
applied to them based on the values of the LCS's which
bracket the group.
Noise
Noise is that component of the instrument response which
is random, unpredictable, and non-deterministic. Changes
in the level of the response due to changes in a factor
settings (cylinder 1 to cylinder 2, day 1 to day 2, hook-up
replication 1 to hook-up replication 2, etc.) would NOT
be considered "noise". Changes in the level of the
response due to deterministic, structured, systematic
time-induced effects (local drift) would also NOT be
considered as "noise". Noise is whatever is left over
when all of the deterministic, predictable components
have been accounted for and subtracted out.
The noise of a system is most commonly observed in the
non-constant, unpredictable sequence of instrument
readings which result when multiple measurements are made
under fixed experimental conditions (same cylinder, same
time of day, etc.) The noise of a system commonly tends
to a locally unpredictable but globally regular frequency
pattern which is best summarized and described by
probabilistic distribution models. The most common
"noise model" is normal (= Gaussian).
Outlier
An "outlier" is an instrument response (a data point)
which "behaves" as if drawn from a population different
from the rest of the data. An underlying assumption in
the statistical analysis is that after the systematic
factors have been accounted for, the data as a whole will
"behave like" they came from a common distributional
population, and the certificate value being produced will
be a representative summary statistic of that common
population. Undetected outliers have the effect of
biasing the summary statistics.
More broadly, "outlier" may refer to either an
1) instrument response value (as above); or a
2) cylinder.
Definition 2 (cylinder) is less common and to designate n
outlying cylinder one must be explicit (e.g., "cylinder
outlier 17", as pposed to only "outlier 17"). Definition
1 (instrument response value) is much more common and is
the preferred definition hen the "outlier" is otherwise
unqualified.
Outlier detection and eradication is an important
component of both the chemical and the statistical
analysis.
Reproducibility
The chemical analysis process is said to be reproducible
if multiple readings on a given cylinder, taken over the
multi-day lifetime of the experiment, yield response
values which are chemically and statistically equivalent.
The most common method of assessing reproducibility is to
take readings on the lot control standard (LCS) multiple
times. If there are no apparent differences in the
response over these mutliple runs, then the process is
said to be "reproducible". If a process is not
reproducible, then the usual cause is instrumental or
procedural.
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Glossary A-B-C
..........A..........
ANOVA (Analysis of Variance)
A statistical technique used to determine
which factors significantly effect the
response of interest (e.g., concentration).
ASCII
A format for characters within files. ASCII is an
acronym for American Standard Code for Information
Interchange. The advantage of using ASCII format is
portability and ease of I/O across all software
packages.
Add in Quadrature
A method for obtaining a summary uncertainty
statistic which consists of square rooting the sum
of the squared uncertainty components. Thus, for
example, uncertainties U1, U2, and U3 are "added in
quadrature" to obtain a single summary statistic U
as follows:
U = sqrt(U1*U1 + U2*U2 + U3*U3)
Adjust Data
To modify the contents of (typically) the original
raw data set by removing outliers, correcting
mis-read data, and/or by collecting more data. The
basis for such modification can be chemical,
procedural, or statistical.
Analysis
Analysis has 2 definitions: chemical analysis and
statistical analysis:
1) Chemical analysis consists of all
concentration measurement operations and
calibration operations needed to obtain raw
concentration readings;
2) Statistical analysis consists of all
numeric and computational procedures (both
quantitative and graphical) to ascertain the
quality of the data, the validity of underlying
assumptions, and the determination of final
certificate values.
Analysis Issue
Area
Automate
To identify and remove as many of the "manual" steps
in the chemical/statistical analysis.
Such automation requires
1) hardware & computerization
2) software
3) process flowchart which
identifies all possible "states" &
decision points of the process along with
detailed instructions as to what to do
when each state occurs.
..........B..........
B0, B1, B2, ressd.
Output statistics from the calibration regression.
For linear regression, the model is Y = B0 + B1*X.
For quadratic regression, the model is Y = B0 + B1*X + B2*X**2
B0 is the intercept or the additive coefficient;
B1 is the slope or the linear coefficient;
B2 is the quadratic coefficient;
ressd is the residual standard deviation
(it is a measure of the goodness of fit of the linear or
quadratic fit).
Batch
A batch is the group of 50 to 100 gas cylinders
produced and certified together as NTRM's.
In general, batch refers to a homogeneous set.
In regard to the gas cylinders, batch referes to
the set of cylinders that are presumedly homogeneous
because their production was in a contiguous block of time;
such a batch is typically of about 50 cylinders and we speak
of a single product batch consisting of these 50 cylinders.
In regard to chemical analysis, "batch" may refer to
a given replicate of all 50 cylinders. The complete
chemical analysis normally has a given cylinder (out
of the 50) being processed (measured) about 3 times.
Processing each of the 50 cylinders exactly once may
take a few days and as such would be referred to as
the first batch (over time). Processing the 50
cylinders a second time would be time batch 2.
Processing the 50 cylinders a third time would be
time batch 3. An implicit assumption is that there
is no difference in the measured concentrations
across the 3 time batches. This assumption should
be checked and verified.
Batch Control Standard (= Lot Control Standard)
This is a representative cylinder chosen from the batch
of cylinders to be certified. It will be used for intercomparison
by the other cylinders in the batch; it will also be
used for intercomparison by the primary standard.
The purpose of the batch control standard is to
detect and assess time drift.
Between-set effect
A statistically significant difference between
2 or more sets of data. If the
sets came from different days, for example, then
it would be said that "day has an effect",
or that "there exists a between-day effect".
Block Plot
A graphical data analysis technique to determine if
a factor (e.g., cylinder) is statistically significant
(yes/no), and if that significance holds
locally: for only some settings of other factors (e.g., day); or
globally: for all settings of other factors (e.g., day).
Bracket the Target
Primary standards chosen
to be both above and below the nominal value
of the SRM are said to "bracket the target".
Experiment design questions in this regard are
1) how many primary standards to choose?
2) how far above and below?
Break
Any interruption (coffee break, lunch break, end of day,
power outage, etc.)
which disrupts the physical flow of data during
the chmeical analysis process.
Break Set (1, 2, 3, ...)
The set of chemical measurements collected in the interim
between 2 breaks.
..........C..........
CO
Carbon monoxide. This is a colorless, odorless gas.
toxic? stable?
NIST provides CO SRMs as follows:
xxx
xxx
CO2
Carbon dioxide. colorless gas
toxic? stable?
NIST provides CO2 SRMs as follows:
xxx
xxx
CU (see Certificate Uncertainty)
CV (see Certificate Value)
Calibration
In general, this is the process whereby a
high-accuracy estimate of some characteristic (such
as concentration) of an artifact (such as a gas
cylinder) is inferred by relating (through a
calibration curve) the readings from a
lower-accuracy device (such as a gas chromatograph)
to the readings from higher-accuracy devices (via
primary gas standards).
For gas cylinder SRMs, this process has several steps:
1) choice of the several primary standards to use
2) choice of an appropriate calibration model/curve
to fit when data is gathered;
3) estimating the coefficients of the calibration model/curve
4) translating (via the calibration curve) the
low-accuracy reading to the corresponding
high-accuracy reading.
Calibration Lot Control Standard
This is the cylinder that is used for intercomparison
during the calibration to the primary standard.
In practice the calibration lot control standard is
physically the same cylinder that is used as the lot
control standard.
Calibration Curve
A fitted mathematical model used for calibration purposes.
A fitted model is one in which the theoretical coefficients
of the model have been replaced by actual values as
estimated from data.
Calibration Model
A mathematical form (equation) which is used for calibration
purposes. The mathematical models most commonly
used for calibration are
1) constrained linear: straight line through origin;
2) floating linear: straight kine with interecept anywhere;
3) quadratic.
Certificate Uncertainty (CU)
An SRM certificate has 2 entries:
1) a certificate value (CV) which gives the best estimate
for the concentration of the gas herein; and
2) a certificate uncertainty (CU) for the certificate value.
Statistical theory separates the uncertainty value
into systematic and random components.
ISO9000 recommendations separate the uncertainty value
into "Type A" and "Type B" components.
If a gas cylinders SRM carries the values 3.14 +- .07
then the .07 is to be interpreted as follows:
It is expected that the true (unknown) concentration
within the cylinder is within the certificate uncertainty .07
of the certificate value 3.14.--that is to say, the true value
is expected to be between 3.07 and 3.21.
Certificate Value CV and CV(i)
An SRM certificate has 2 entries:
1) a certificate value (CV) which gives the best estimate
for the concentration of the gas herein; and
2) a certificate uncertainty (CU) for the certificate value.
If a gas cylinders SRM carries the values 3.14 +- .07
then the 3.14 is to be interpreted as follows:
3.14 is our bstatistical est estimate of the true
concentration in the cylinder.
xxx
The CV with no subscript implies global
certification was done. The CV with a subscript (as
in CV(i)) implies individual certification was done.
The certificate value is computed from the primary
standard calibration.
For global certification, the certificate value CV may be
(depending on circumstances) computed as
CV = Xhat
CV = Xhat(i)
CV = XhatCLCS * Rbar
For individual certification, the certificate value CV(i) may be
(depending on circumstances) computed as
CV(i) = Xhat(i)
CV(i) = XhatCLCS * Rbar(i)
Certification Experiment
The in toto chemical analysis and statistical analysis protocol
that is carried out in order to attach certificate
values and uncertainties for an SRM.
Chemical Analysis
Chemical analysis consists of all concentration measurement
operations and calibration operations needed to obtain raw
concentration readings.
Coded Cylinder ID (1 to 50)
A positive integer (typically 1 to 50) which is attached
to each cylinder in a lot of cylinders to be certified.
The coded cylinder ID is useful in simplifying the statistical analysis.
The coded cylinder ID is to be contrasted with the physical
cylinder ID which is assigned by the cylinder manufacturer
and is hard-stamped onto the cylinder identification plate.
Coded LCS ID
The coded cylinder ID (between 1 and 50) of the
lot control standard.
Comma-separated
a collection of data such that each number on line (record)
is separated from the next data point by a comma.
Compare XhatCLCS for current time
Compare concentrations for current time
Computation Box
Concentrations for prior time.
Concentrations of LCS at time 1
Concentrations of LCS at time 2
Current Data
Cylinder & (Day or Break or LCS Set) Significant?
Cylinder Batch (1 to 4)
Cylinder ID
A number or an alphanumeric mix which uniquely
identifies a given cylinder.
Cylinder IDs are of 2 types:
1) coded cylinder id;
2) physical cylinder id.
Cylinder Significant?
Cylinder
Cylinder i
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Glossary D-E-F
..........D..........
DAN
An acronym for "Data Analysis".
Data analysis refers to all statistical procedures that
are applied to the data after such data
has in fact been collected. In contrast, see DEX.
DEX
An acronym for "Design of Experiment".
DEX refers to those choices, strategies, and procedures
that are executed prior to the collection of any data.
The purpose of a good design of experiment is to assure that
1) the SRM objectives of the experiment
are attainable;
2) the conclusions from the experiment are
valid, uncontaminated, supportable, and repeatable;
3) the experiment provide low-variability estimates
of the desired parameters;
4) the experiment be conducted in as
efficient and inexpensive fashion as possible.
DEX Issues
DEX Recommendation
Data
Data Analysis
Data Analysis Protocol
Data File Format
Data File Recommendations
Data File Routinization
Data Manipulation
Data Reformatting
Data Separator
Dataplot
Date
Date
Day & Break or Day & LCS Set significant?
Day (1, 2, 3, ...)
Decay
Decision Point
Degrees of Freedom
Dependent Variable
Designed experiment
Developing the SRM
Df
Distinct Calibration Concentration
Distinct Calibration Concentrations
Distinct X
Distinct X's
Drift
Drift (= between-set effect)
..........E..........
EU = Expanded Uncertainty (global)
EU(i)= Expanded Uncertainty for Cylinder i
Effect
Enter RUPS = Relative uncertainty of the primary standard
Enter the coded ID number (1 to 50) for the
Estimated intermediate lot control standard values Lhat(i)
Excel
Experiment Design
Experimentalist/operator
Experimentalist/operator
..........F..........
F Test
Fabricating the SRM
Factor
Factor Significance
Factor Having an Effect
File
File Name
File name on line 1
Fit
Flowchart
Format
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Glossary G-H-I
..........G..........
GC
Gas Chromatograph
Gas
Gas Chromatograph Port (1 to 16)
Gas ID
Global Certification
Global Decay
Global Drift
Global or Individual Certification
Globally Stable Gas
Graphical Data Analysis
Graphical Residual Analysis
Group
"Group"
..........H..........
H2S
Hydrogen sulfide (an unstable gas)
Header
The information provided at the beginning of a data file to describe
its content.
Heterogeneous
Hidden Character
Computer file information is typically of the alphabetic and
numeric variety. Some characters, however, may be invisible
(hidden)--for example, the tab character, the escape character,
etc. In particular, out of the 128 members of the ASCII character set,
the first 32 of them are hidden (not visible). For ease of I/O
in the statistical analysis, it is recommended that no hidden
characters be used in the data file. In particular, the use of
the tab character (since it cannot be seen but only its effect
seen) is to be discoraged--a better choice would be to literally
put in the blank spaces rather than the tab.
Homogeneous
In general, homogeneous refers to consistency across elements.
In particular for gas cylinders SRMs, homogeneous refers to
a consistency across the cylinders of the batch to be certified.
A gas cylinder batch is homogeneous if the concentration among
the cylinders of this SRM batch are not significantly different.
When the cylinders are homogeneous, the batch may be globally
certified--that is a common gas concentration value is determined
and that common value is assigned to all cylinders in the batch.
Homogeneous SRM
A homogeneous SRM is one in which the batch of cylinders to be
certified were homogeneous. In such case, the cylinders are
globally certified (with a common number) as opposed to
individually certified (with cylinder-specific numbers).
..........I..........
Independent Variable X: Primary Standard Concentration
Independent Variable
The variable "x" in a regression model (also known as
the regressor or predictor variable).
Individual Certification
The certification method for an inhomogeneous gas
cylinder SRM where certification are performed separately for each cylinder.
Inhomogeneous
In general, inhomogeneous refers to inconsistency
across elements. In particular for gas cylinders
SRMs, inhomogeneous refers to an inconsistency
across the cylinders of the batch to be certified.
The most common form of inconsistency is
location-inconsistency: one or more of the cylinders
out of the batch of 50 has a concentration which is
higher (or lower) than the remaining cylinders. A
less common form of inconsistency is
variation-inconsistency: one or more of the
cylinders out of the batch of 50 has a distribution
of multiple concentration readings which have a
spread which is higher (or lower) than the remaining
cylinders.
If a batch of cylinders is said to be inhomogenous
(with no explanation) then by default it is
location-inconsistent.
Instability
The quality or state of being unstable.
Instrument
A device used to produce response (peak area, voltage, ...) for
each cylinder.
Intercept
The constant term in a model.
Interpreting Output
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Glossary J-K-L
..........J..........
..........K..........
..........L..........
LCS
Lot control standard cylinder.
LCS Cylinder ID
LCS ID
LCS Set
Least Squares Regression
The statistical method for determining the regression equation for
which the sum of squares of the residuals is minimized.
Lhat
Estimate of the variable "L".
Lhat(i)
The estimated (usually by linear interpolation) ith intermediate
response for lot control standard cylinder.
Linear Model
The regression model of a line.
Linear-Through-Origin Model
A linear model with zero intercept.
Local Drift
Local Decay
Lot Control Standard Cylinder
The representative cylinder chosen from the lot
of cylinders for each SRM to be intercompared to the other cylinders of the lot
and to the primary gravimetric standards.
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Glossary M-N-O
..........M..........
Mean Response
The expected value of a response (peak area, voltage, ...).
Mean Square Error
The expected value of the square of an error.
Minimal Engineering Significant Difference
Model
A mathematical description of an affair.
Multiple Calibration Experiments
..........N..........
n(i) = number of "groups" within cylinder i
n(i) = number of "groups" within day i
n(i) = number of ratios for cylinder i
nC = number of cylinders
nD = number of days
nG = number of "groups"
nmin = min{n(i)}
nR = number of ratios
NO
NTRM
Nominal Value
..........O..........
Omit data
Omit/correct data
Operating System
Optimize a process
Organics
Outlier
Outliers in the Lot Control Standard
Outliers in the Primary Standard Data
Outliers in the Test Cylinders
Outliers in the Ratios
Output Summary File
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Glossary P-Q-R
..........P..........
Parsimony
Parameters
PC 95
PC/Linix
PC/Unix
PC/Windows 95
PC/Windows NT
Pc/Windows 3.1
Physical cylinder ID
Platforms
Pool the 2 data sets.
Port Significant
Preprocess
Primary Standards Calibration Data
Primary Standards Calibration Data for Prior Time
Primary Standards Data
Prior Data
Process
Propagation of error
Propane
Protocol
..........Q..........
Quadratic : Xhat = ...
Quadratic : Xhat(i) = ...
Quadratic Model
Quadrature
Quantitative Data Analysis
..........R..........
REU
Relative Expanded Uncertainty
RUC
Rel. unc. of calibration = RSD(Xhat(i))
RUC
Rel. unc. of calibration = RSD(Xhat)
RUC
Rel. unc. of calibration = RSD(XhatCLCS)
RUGM
Rel. uncertainty of Rbar = SD(Rbar) / Rbar
RUGM
Rela. unc. of grand mean = RSD(Rbar(i))
RUGM
Rela. unc. of grand mean = RSD(Rbar)
RUGM(i)
Rel. unc. of Rbar(i) = SD(Rbar(i)) / Rbar(i)
RUPS
Relative Uncertainty of Primary Standard(s)
Ratio Statistics
Ratios
Calculated ratio of response for sample cylinder,
divided by measured or interpolated response for lot control
standard cylinder. Here "response" is a generic term for
"voltage" or "peak area" or whatever the instrument provides
as a measured value.
Raw Data
Actual detailed data produced by the instrument,
before ANY interpolation or averaging is done.
Rbar
Average or a variable whose name is "R" (a ratio)
Average of the nC Rbar(i)
Average of the nD day averages
Average of the nG Rbar(i) averages
Average of the nR ratios
Rbar(i)
Average of ratio data that belong to a defined
subgroup labeled "i". The index "i" may denote a day, or a
"group" associated with a given pair of LCS readings, or the
I.D. of a given cylinder, as determined by context.
Rbar(i,j)
Average of ratio data that belong to a defined
subgroup labeled "i,j". In the case of two indexes, each
index is used to label members of two different types of
"group." For example, "i" may denote "day" while "j"
denotes "cylinder ID." Or, depending on context, "i" could
denote "cylinder ID" and "j" could denote "group associated
with a pair of LCS readings."
Regression
The statistical operation of fitting a line or
curve by least squares. The method used to calculate a
slope, intercept, or the coefficients of a quadratic curve.
Replicate
Repeated value, reading, or measurement (depending
on context).
Residual Analysis
The (usually graphical) process of checking
the validity or appropriateness of a regression. Outliers
may be identified. The decision may be made as to whether a
straight line is adequate, as opposed to a quadratic.
Residual Standard Deviation
Standard deviation representing
the typical scatter of data around a regression line (or
curve).
Response Variable Y
Used to assign some part of the data as a
variable named "Y". This may be a voltage, or peak area, or
a calculated ratio relative to the LCS. Identifying this
particular variable as the "response" and naming it "Y"
implies that this variable will be used in a regression
model as the dependent variable, represented as a linear (or
quadratic) function of some other variable "x".
Routinization
Making it possible to complete a statistical
analysis by formally specifying an algorithm (or computer
program or stepwise procedure) by which the necessary steps
can be accomplished.
Run
A generic term that refers to the (chemical or laboratory)
operation required to produce one number in a table of data.
The operational meaning of a "run" usually depends on the
context of the data table under discussion.
Click here to return to alphabetic list
Glossary S-T-U
..........S..........
SAS
Brand name of a large statistical software package.
SD(R)
Standard deviation (actually standard uncertainty) of
the quantity "R" inside the parentheses.
SD(Rbar)
Standard deviation (actually standard uncertainty) of
the quantity "Rbar" inside the parentheses. The meaning of
"Rbar" must be decided from context.
SD(Rbar(i))
Standard deviation (actually standard uncertainty)
of the quantity "Rbar(i)" inside the parentheses. The
meaning of "Rbar(i)" must be decided from context.
SD of the nD day averages
SD of the nG Rbar(i) averages
SD(i) / sqrt(n(i))
SDRbar(i)
SD of the n(i) Rbar(i,j) for cylinder i
SDpool
"pooled" standard deviation obtained by combining (by
weighted root mean square averaging) several independent
standard deviations obtained from different subsets of the
data.
Separator
Tabs or commas or spaces used to separate numbers on
the same line in a data file. Spaces are preferred.
Significant Factor
A factor (as Day, or Break, or LCS group,
or Cylinder) that is determined to be a statistically
significant contributor to the variability of the data. For
example, if the factor cylinder is significant, the it means
that the cylinders differ in concentration (from each
other). If Day is significant, then there is a detectable
amount of between-day variability that is not accounted for
by the within-day variability.
Significant Factors (including cylinder)
Significant Factors (mode)
Significant Cylinder
Slope
SO2
Software
Spectroscopy
SRM
Scope
Stability
Constancy. For a cylinder, this refers to constancy
of concentration over a longish period of time (6 months or
a year). For an instrument, this would refer to lack of
drift during measurement.
Stable Gas
Standardized Reference Material
Standardized Data File Format
Standardize
Statistically Significant
Statistic Tools
Statistical Analysis
Sun
A unix computer workstation used by many staff in the
Statistical Engineering Division.
..........T..........
t TEST
Tab Character
Test Cylinder
The Calibration Lot Control Standards may drifted,
The process is complicated.
There is a drift in the concentration ??
Time 1
Time 2
Time effect?
Time of Day
Time of day not recorded: R(i) = Y(i) / Lhat(i)
Time of day recorded: R(t) = Y(t) / Lhat(t)
Turn-Around Time
..........U..........
Uncertainty Components
Unix
Unstable Gas
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Glossary V-W-X-Y-Z
..........V..........
Variable Data File Format
Vectorize
Vendor Data
Voltage
..........W..........
Web Page
What model to select?
Within-data-line separator = space(s)
Within-line separator
Write #1: Summary Information
..........X..........
Xhat = finverse(Rbar)
Xhat(i) = finverse(Rbar(i))
XhatCLCS = finverse(YbarCLCS)
XhatCLSC for prior time
..........Y..........
YbarCLCS = average of the Calibration Lot Control Standards
YhatCLCS
..........Z..........
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