. Author manuscript; available in PMC: 2008 May 14.

Published in final edited form as: Environ Sci Technol. 2007 Oct 15;41(20):7152–7158. doi: 10.1021/es071041z

TABLE 4.

SEM Regression Results for Select VOCs and Aldehydes^a

eq 1: $ln (WorkAreaConc) = β_{10} + β_{11} ln (YardBackground) + β_{12} Job + ε$
	benzene (n = 76)	1,3-butadiene (n = 75)	toluene (n = 75)	formaldehyde (n = 70)
yard background	0.79^b (↑51%)	0.48^b (↑76%)	0.46	0.35
job	0.53^b (↑70%)	0.99^b (↑169%)	1.19^b (↑229%)	0.99^b (↑169%)
constant	−0.26	−0.81^b	0.34	1.55
RMSE	0.63	0.71	1.22	0.84
R²	0.38	0.25	0.20	0.18
eq 2: $ln (YardBackground) = β_{21} (Temperature) + β_{22} (Windspeed) + β_{23} (RoadDistance) + β_{24 - 6} (RegDummy) + η$
	benzene	1,3-butadiene	toluene	formaldehyde
temperature	0.01	−0.05^b (↓41%)	0.01	0.02^b (↑23%)
windspeed	−0.09^b (↓24%)	−0.09^b (↓24%)	−0.15^b (↓39%)	−0.04^b (↓13%)
road distance	−0.0004^b (↓51%)	0.0002	−0.0003^b (↓42%)	−0.0001
region 1 (Midwest)	0.99^b (2.69)	−0.05	2.15^b (8.58)	1.22^b (3.39)
region 2 (Northeast)	1.03^b (2.80)	−1.04^b (0.35)	2.07^b (7.92)	1.37^b (3.94)
region 3 (West)	1.45^b (4.26)	0.06	2.78^b (16.12)	1.08^b (2.94)
constant^c	n/a	n/a	n/a	n/a
RMSE	0.40	0.68	0.53	0.37
R²	0.45	0.83	0.80	0.90

In parenthesis for significant coefficients are % changes in dependent variable prompted by a one-standard deviation rise in the predictor variable or % difference between mechanic shop and loading dock for job. For regional census variables, multiplicative effect sizes are presented.

Significant at 5% level.

The constant has been dropped from eq 2 since all three regional dummy variables are included in the model. This does not effect the coefficients for the other variables, only the interpretation of the regional variables (hypothetical null used as baseline).