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Table 1 Nitrogen dioxide concentrations (ppb) during DNC and non-DNC weeks, stratified by a priori traffic classification.

From: The air quality impacts of road closures associated with the 2004 Democratic National Convention in Boston

Category Median concentration and range, DNC Median concentration and range, non-DNC 1 Median concentration ratio (DNC/non-DNC) and range
1 – Hypothesized decrease (n = 7) 7 (3 – 16) 10 (6 – 20) 0.58 (0.27 – 2.0)
2 – Hypothesized increase (n = 9) 14 (7 – 19) 12 (3 – 15) 1.15 (0.51 – 1.88)
3 – Hypothesized no change (n = 11) 11 (6 – 19) 12 (7 – 17) 0.88 (0.82 – 1.23)
4 – Unclear impacts a priori (n = 7) 7 (6 – 9) 12 (4 – 18) 0.70 (0.38 – 2.4)
  1. 1 Average of concentration the week before and after the DNC