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According to EPA guidance, 24 distinct elements can
be included in a QAPP, although not all elements may be necessary for all
programs. Which elements you end up including in your QAPP depends on your
project's goals, objectives, scope, data uses, and on the guidance you receive
from your state or EPA regional quality assurance contacts. The 24 elements are
grouped into four overall categories:
A. Project Management
B. Measurement/Data Acquisition
C. Assessment and Oversight
D. Data Validation and Usability
There are several basic Quality
Assurance and Quality Control concepts to understand and address in a
QAPP. The first is called the
"PARCC" Parameters. Taken
together, the terms Precision, Accuracy, Representativeness, Completeness, and
Comparability, comprise the major data quality indicators used to assess the
quality of your data. It is essential to understand these terms and to address
them in your QAPP.
It is equally
important to understand the terminology of quality assurance and quality
control in order to develop a QAPP. Key definitions include:
Precision -- the
degree of agreement among repeated measurements of the same characteristic. It
may be determined by calculating the standard deviation, or relative percent
difference, among samples taken from the same place at the same time.
Accuracy -- measures
how close your results are to a true or expected value and can be determined by
comparing your analysis of a standard or reference sample to its actual value.
Representativeness -- the
extent to which measurements actually represent the true environmental
condition or population at the time a sample was collected.
Completeness --the
comparison between the amount of valid, or usable, data you originally planned
to collect, versus how much you collected.
Comparability -- the
extent to which data can be compared between sample locations or periods of
time within a project, or between projects.”