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APPENDIX E
DATA QUALITY INDICATOR DEFINITIONS and EXAMPLES
Data Quality Indicator
Meaning
QC Measures
Precision
Agreement among repeated
measurements under identical, or
substantially similar conditions
•
Field duplicates or splits
•
Lab duplicates/replicates
•
Can be within same organization or among
organizations using the same or different
methods
Bias
Systematic or persistent
distortion of a measurement
process that causes errors in one
direction
•
Instrument calibration standards
•
Lab QC spikes
•
Matrix spikes & duplicates)
Accuracy
Overall agreement of a
measurement to a known value -
includes a combination of
random error (precision) and
systematic error (bias) in both
sampling and analysis operations
•
Matrix-specific standard or certified reference
materials
•
Spiked matrix samples
Representativeness
The degree to which data
accurately and precisely
represent a characteristic of a
population or condition
•
No specific QC tools to measure
•
Evaluate if samples were collected and
measurements made in such a way that they
reflect the population of interest (as specified
in the QAPP)
Comparability
Measure of confidence that one
data set can be compared to
another and combined for the
decision(s) to be made
•
Split samples; existing data
•
Compare population targeted by sampling
techniques; sample collection, handling,
preparation, & analysis procedures; holding
times, stability issues, QA protocols
Completeness
The amount of valid data needed
to be obtained from a
measurement system
•
# of valid results vs. the number determined to
be necessary during project planning (as
specified in the QAPP)
Specificity
Correct identification of the
parameter you are targeting
•
Retention times
•
Ion abundance ratios
•
Confirmation analyses
•
Peak shape
Detection and
Quantitation
The ability to
•
Determine if it is there or
not
•
Distinguish between
responses representing
different concentrations of
interest
•
Method Detection Limit (MDL) or equivalent
•
Signal to noise ratios
•
Calibration range
•
Analysis of samples at/near quantitation limit
•
Well below action level