PRECISION. From time to time COUNTY may submit to CONTRACTOR, without prior notification or identification as such, two or more samples of identical composition, or differing in composition by a known factor established by volumetric dilution. Unsatisfactory replicate analyses, as defined in Paragraph D, below, may be cause for cancellation of this contract by COUNTY, and/or for penalty discounts of CONTRACTOR’s invoices, in accordance with the provisions of that paragraph.
PRECISION. The precision, defined as 2.5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, shall be no greater than 1 per cent of the full scale concentration for a measurement range equal or above 155 ppm (or ppmC1) and 2 per cent of the full scale concentration for a measurement range of below 155 ppm (or ppmC1).
PRECISION. The precision studies were performed using three lots of Cascade Abrazo PT-WB Level 1 and Level 2 controls and one lot of Cascade Abrazo PT-WB cards. The studies were performed by multiple non-laboratorian operators (POC) at three sites across 6 Cascade Abrazo analyzers. Each operator performed 2 runs per day, 2 tests per run on each lot of Abrazo PT-WB test controls over a period of 20 days. *Precision studies were performed according to EP5-A2.6 References
PRECISION. The precision, defined as 2.5 times the standard deviation of 10 repetitive responses to a given nominal flow, approximately in the middle of the calibration range, shall not exceed 1 per cent of the maximum flow at which the EFM has been calibrated.
PRECISION. Collocated precision results for units #121 and #123 are summarized in Table 3-3. A portion of this dispersion is due to a bias between the instruments. Transforming the hourly data for #123 using a constrained linear least squares regression of #123 on #121 (slope 0.881) yields a collocated precision of 2.9 μg/m3 (13.0%).
PRECISION. Do the data have an acceptable margin of error? Yes No Comments Recommendations for improvement:
PRECISION. In 2006 a subset of samples were reanalyzed by DRI using a newly-commissioned XRF instrument which replaced the XRF instrument used for the first two years of St. Louis – Midwest Supersite samples. This analysis provides a stringent test for the analysis methods contribution to collocated precision since different instruments were used. The last four columns of Table 4-5 report the comparisons for samples with the first analysis concentration at least ten times the DRI-reported MDL. Twenty-three of the forty reported elements had no concentration values exceed this threshold. Relative precision was better than 10% for all elements with at least five concentration values above the threshold.
PRECISION. Precision estimates for PILS-IC, based on both propagation of precision for the intrinsic measured parameters and from collocated measurements, have been reported elsewhere (Xxxxxx et al. 2003). In contrast to that relatively short duration study with stable operating conditions, the East St. Louis deployment focused on sustained, routine measurements during which additional sources of imprecision can surface. Numerous factors influencing PILS-IC measurement precision are described by Xxxxxxxxxxx (2005; Chapter 5), which focused on a newer-generation version of PILS compared to the version deployed for the 2001-2002 measurement program. We have not fully assessed how the factors identified by Xxxxxxxxxxx (2005) affect the quantitative precision estimates for the earlier generation measurements and rely upon bias and comparability metrics to document the data quality.
PRECISION. The movable measurement platform (satellite site shelter) was periodically deployed at the core site for collocated measurements with the results summarized in Table 3-2. These metrics are based on all data. Including only those concentration values exceeding ten times the MDL reported in Table 3-1 yields collocated precision of 1.0 μg/m3 (4.6%) for PM1.0 (N = 3) and 2.0 μg/m3 (9.5%) for PM2.5 (N = 10). All concentration values were greater than ten times the MDL for the collocated PM10 data set. In addition to the completely independent measurements, two PM2.5 samples were collected in parallel on most days. The last row of Table 3-2 shows the collated precision for those measurements which shared the same pump and timer but had independent flow control elements. This measurement captures a subset of the overall collocated variability. Bias and Comparability. One quality check for the PM gravimetric mass data is to test whether PM1.0 < PM2.5 < PM10 mass within the measurement uncertainty. Figure 3-1 shows scatter plots for PM1.0 and PM2.5 (Fig. 3-1a), and PM2.5 and PM10 mass (Fig. 3-1b). There were four cases where PM1.0 exceeded PM2.5 (by 0.5, 0.7, 0.8, and 1.0 μg/m3), and one case where PM2.5 exceeded PM10 (by 0.2 μg/m3). Assuming the 0.5 μg/m3 absolute precision estimated from PM2.5 samplers from the same sampling system (last row of Figure 3-2), these cases can be explained by measurement error. In addition to the above Supersite platform measurements, the Illinois EPA (IEPA) operated a full suite of NAAQS compliance monitors, including a PM2.5 FRM, at the 13th & Tudor (East St. Louis) at the monitoring site which shared the same physical footprint as the Supersite. The IEPA and Supersite PM2.5 gravimetric mass measurements were independently conducted at all levels (different field staff, audit devices, handling and storage facilities, and gravimetric mass analytical laboratories). IEPA samplers and continuous analyzers were included in the systems and performance audits conducted by DRI. Comparability between the IEPA FRM and Supersite Harvard Impactor (HI) gravimetric mass measurements are shown in Figure 3-2a for the period 4/14/01 through 3/31/2003 and excluding one value at (95.7, 88.8). A reduced major axis regression yielded: FRM = (0.92 ± 0.05)× HI + (−0.8 ± 0.7 μg / m3 ) The FRM and HI measurements are comparable with the HI biased high. This bias likely arises from differences in samplers, including but not limited to the impactor cutpoint ...
PRECISION. A statement of the repeatability of a measure. See also, accuracy.
