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. 2014 Aug 5;13:63. doi: 10.1186/1476-069X-13-63

Table 1.

Bias and precision statistics from cross-validation (CV) of PM 2.5 , PM 10 , and PM 2.5–10 models from 1999-2007

Pollutant RegionA Monthly values
 Spatial CV R2G
NB N excludedC Model R2D CV R2 InterceptE SlopeE NMBF (%)F CVMAEF NMEF (%)F
PM2.5
 All
 108,718
 4
 0.84
 0.77
 0.3
 0.87
 −1.6
 1.61
 14.3
 0.89
 
 Northeast
 24,318
 0
 0.85
 0.81
 0.2
 0.92
 −1.4
 1.44
 11.4
 0.88
 
 Midwest
 15,767
 0
 0.85
 0.81
 0.2
 0.91
 −0.7
 1.31
 10.6
 0.89
 
 Southeast
 24,201
 1
 0.88
 0.83
 0.2
 0.92
 −0.4
 1.31
 9.7
 0.82
 
 Southcentral
 12,762
 0
 0.79
 0.72
 0.2
 0.89
 −0.6
 1.44
 14.1
 0.83
 
 Southwest
 13,448
 2
 0.79
 0.69
 0.4
 0.81
 −5.5
 2.65
 26.8
 0.83
 
 Northwest
 9,052
 0
 0.65
 0.50
 0.7
 0.62
 −4.6
 2.07
 28.9
 0.62
 
 Central Plains
 9,170
 1
 0.72
 0.60
 0.4
 0.81
 −2.8
 1.66
 23.2
 0.81
PM10
 All
 104,509
 22
 0.71
 0.58
 0.7
 0.77
 −5.1
 5.21
 24.4
 0.69
 
 Northeast
 16,982
 0
 0.67
 0.57
 0.7
 0.76
 −4.7
 4.17
 19.8
 0.68
 
 Midwest
 10,088
 0
 0.63
 0.48
 0.9
 0.71
 −6.0
 4.82
 21.2
 0.56
 
 Southeast
 20,316
 0
 0.62
 0.49
 0.7
 0.76
 −4.0
 3.89
 17.6
 0.46
 
 Southcentral
 8,092
 0
 0.61
 0.45
 0.8
 0.74
 −6.0
 6.24
 27.4
 0.44
 
 Southwest
 24,050
 19
 0.76
 0.62
 0.7
 0.79
 −4.7
 6.92
 27.8
 0.72
 
 Northwest
 5,943
 1
 0.59
 0.49
 0.8
 0.71
 −1.6
 5.33
 30.2
 0.72
 
 Central Plains
 19,038
 2
 0.61
 0.50
 0.8
 0.71
 −7.6
 5.11
 31.3
 0.66
PM2.5-10H
 All
 41,098
 1,936
 0.67
 0.52
 0.6
 0.76
 −3.2
 4.18
 38.9
 0.61
 
 Northeast
 8,375
 423
 0.49
 0.35
 0.9
 0.58
 −8.9
 3.46
 42.7
 0.53
 
 Midwest
 4,567
 233
 0.61
 0.43
 0.7
 0.70
 −1.5
 3.72
 34.4
 0.49
 
 Southeast
 7,178
 359
 0.45
 0.28
 0.5
 0.75
 −4.2
 3.02
 38.0
 0.36
 
 Southcentral
 3,614
 23
 0.61
 0.40
 0.9
 0.62
 −11.4
 5.63
 44.6
 0.33
 
 Southwest
 9,237
 296
 0.74
 0.56
 0.5
 0.81
 −1.6
 5.64
 36.6
 0.64
 
 Northwest
 2,579
 340
 0.55
 0.47
 0.3
 0.92
 18.1
 3.97
 48.2
 0.58
  Central Plains 5,548 262 0.56 0.41 0.6 0.74 −2.3 3.87 39.8 0.61

ACorresponds to regions shown in Figure 1.

BIncludes data from CV sets one through nine; see text for details.

CThree PM2.5 values above 70 μg/m3 (>99.99th percentile) and one low value, as well as 22 PM10 values above 150 μg/m3 (>99.99th percentile) were excluded from CV statistics as outliers. Extreme values may have been due to local events such as wildland or other fires, dust storms, etc.

DCalculated on the native rather than natural-log scale and among observations used for CV for comparison to the CV R2. For PM2.5–10, predicted levels<=0 were removed.

EFrom major axis regression of predictions on measurements (both are natural-log transformed monthly means); see text for details.

FNMBF is normalized mean bias factor; CVMAE is cross-validation mean absolute error; NMEF is normalized mean error factor; see text for details.

GSpatial CV R2 calculated at 1,245, 1,192, and 512 sites with >35 valid monthly-average measurements for PM2.5, PM10, and PM2.5–10, respectively.

HCalculated as the difference between monthly PM10 and PM2.5 measurements and, separately, monthly PM10 and PM2.5 model predictions. Of the 1,936 values excluded as outliers, 11 were removed due to extreme PM10 or PM2.5 measurements; an additional 1,925 were due to measured or predicted PM2.5–10 below the limit of detection of 0.57 μg/m3 (<3.4th percentile of measured and <1.6th of predicted PM2.5–10).