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Table 1 Overall average pollutant levels for pollutants considered in power simulations, Atlanta, 8/1/98-7/31/99

From: Power estimation using simulations for air pollution time-series studies

Pollutant

Mean

Standard Deviation

25th Percentile

Median

75th Percentile

Maximum

Skewness*

Number of days missing for moving average of lags 0-2

PM2.5 (μg/m³), 24-h average

19.42

9.35

12.50

17.54

24.76

53.24

1.00

31

Total water- soluble PM2.5 metals (μg/m³), 24-h average

0.03

0.03

0.01

0.02

0.04

0.20

2.07

58

Elemental carbon (EC) (μg/m³), 24-h average

2.26

1.74

1.26

1.88

2.60

15.61

2.83

22

Carbon monoxide (CO) (ppmV), daily 1-h maximum

1.47

1.30

0.60

0.98

1.81

9.42

2.27

44

  1. *Skewness was calculated using SAS version 9.2 with the formula: “ n n − 1 n − 2 ∑ i = 1 n w i 3 / 2 x i − x ¯ w s w 3 where n is the number of non-missing values for a variable, x i is the i th value of the variable, x ¯ w is the sample average, s is the sample standard deviation, and w i =1 for all i=1,…,n“[25].