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3)
The MDL is computed as the product of the standard deviation and the critical t-value:
4)
To test for uniform variance, another solution is spiked with a slightly different concentration of the
analyte. Measurements are taken on at least 7 samples of this new solution and results are tabulated as
with the first solution.
5)
An F-test for two sample variance is performed on the two data sets to ensure that the difference
between the variances are "statistically insignificant" (F
stat
< F
crit
).
6)
If determined insignificant, the procedure continues by pooling the two sample variances as follows:
7)
A new critical t-value is looked up using the new amount of degrees of freedom:
8)
The MDL is computed as the product of the new critical t-value and the pooled standard
deviation:
The PQL or RL is the minimum value that can be reported with confidence, i.e., some multiple of the
MDL. The requirements for quantification are more stringent than for detection. A limit of quantification
(LOQ) is generally defined at 5 to 10 times the standard deviation of the noise (or blank) signal. In
practice, PQLs are defined at the lowest concentration in the calibration curve. In this method, the
calibration statistics (e.g., correlation coefficient, confidence intervals, RSD of response factor) ensure
that the PQL represents the same precision and accuracy as other data reported for the analyte.
MERC reports sample data measured below the MDL as ND or non-detect. Sample data measured ≥
MDL but ≤ PQL or RL is reported as estimated data. Sample data measured above the PQL or RL is
reported as reliable data unless otherwise qualified per the specific sample analysis.
A.8.
Special Training/Certification
The MERC QMP (Section 4.0) requires that staff members have the knowledge, skill, and any
professional certifications needed to perform their MERC assignments and that quality management
responsibilities and requirements are understood at every stage of project implementation throughout
MERC (Table 6). The PC is responsible for identifying worker certification needs and ensuring that all
team members are adequately trained.
A.8.1.
General Training Requirements
The general approach to training is to utilize a combination of clearly documented guidance material and
experience from existing or previous staff and supplement these with formal trainings as needed.
Individuals implementing MERC tests must receive, at a minimum, orientation to the project’s purpose,
scope, and methods of implementation. This orientation is the responsibility of the PC.