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. Author manuscript; available in PMC: 2017 May 1.
Published in final edited form as: Environ Res. 2016 Feb 11;147:164–171. doi: 10.1016/j.envres.2016.02.004

Table 2.

Descriptive statistics

Variable N Mean Min. Max. IQR2 Missing
LEVEL 2 Total RR (ln) 58 0.62 0.39 0.05 1.93 0.61 0
 Total RR1 58 2.01 0.96 1.05 6.88 1.16 0
On Road RR (ln) 58 −0.57 0.76 −1.51 1.68 1.33 0
 On Road RR1 58 0.78 0.80 0.22 5.39 0.84 0
Non Road RR (ln) 58 −1.78 0.52 −3 −0.49 0.57 0
 Non Road RR1 58 0.19 0.11 0.05 0.61 0.10 0
Total Diesel PM (ln) 58 0.08 0.67 −0.8 2.07 1.16 0
 Total Diesel PM1 58 1.39 1.21 0.45 7.93 1.39 0
On Road Diesel PM (ln) 58 −0.27 0.77 −1.24 2.01 1.36 0
 On Road Diesel PM1 58 1.07 1.11 0.29 7.49 1.16 0
Non Road Diesel PM (ln) 58 −1.24 0.58 −2.41 0.85 0.59 0
 Non Road Diesel PM1 58 0.35 0.33 0.09 2.34 0.16 0
Total School Enrollment 58 546 129 273 840 192.25 0
% Free/Reduced Price Meals 58 74.06 22.77 15.43 99.43 39.65 0
Student/Teacher Ratio 58 20.21 1.8 15.68 23.73 2.41 0
% Special Education 58 10.97 4.87 .266 27.02 4.89 0
% Teachers with MA Degree 58 24.45 17.46 0 66.5 23.96 0

LEVEL 1 Child Sex 1828 0.5 0.5 0 1 n/a 3.2
Child Age 1856 10.39 0.77 8 13 1 1.7
Free/Reduced Price Meals 1650 0.60 0.49 0 1 n/a 12.6
Teen Mother 1625 0.09 0.28 0 1 n/a 13.9
Mother’s Education 1685 13.07 3.88 1 21 4 10.8
Mother is Hispanic 1666 0.8 0.4 0 1 n/a 11.8
Mother is Black 1694 0.02 0.15 0 1 n/a 10.3
Mother’s English Proficiency 1649 2.17 1.03 0 3 2 12.7
Child’s GPA 1683 3.32 0.66 0.2 4 1 10.9
1

This variable was not used in the statistical models, since a natural log transformation was needed to reduce skewness and kurtosis. It is included here since the values are more meaningful when interpreted than the transformed version.

2

Interquartile range, n/a= not applicable to dichotomous variables