Skip to main content

Advertisement

Table 3 Risk ratios of emergency department visits for pediatric asthma for days in the terminal nodes as compared to the referent group, a Atlanta, Georgia, 1999–2009

From: Classification and regression trees for epidemiologic research: an air pollution example

Terminal nodeb Nc Risk ratio 95% Confidence interval Type of days (pollutant quartiles)
     CO NO2 O3 PM2.5
Referent 131 1.00   1 1 1 1
T1 316 1.10 (1.05, 1.16) 1-4 1,2 1-4 4
T2 279 1.08 (1.03, 1.14) 1-4 3,4 1-4 1
T3 1039 1.05 (1.01, 1.1) 1-4 3,4 1-4 2,3
T4 441 1.07 (1.02, 1.13) 1-4 3,4 4 4
T5 91 1.03 (0.97, 1.1) 1,2 1,2 4 1-3
T6 68 1.07 (0.98, 1.17) 3,4 1,2 4 1-3
T7 76 1.08 (1.01, 1.15) 1-4 3 1-3 4
T8 168 1.07 (1.01, 1.14) 1-4 4 1-3 4
T9 458 1.01 (0.97, 1.05) 1-4 1 1,2 1-3
T10 263 1.04 (0.99, 1.09) 1-4 2 1 1-3
T11 435 1.03 (0.98, 1.07) 1-4 2 2,3 1-3
T12 160 1.02 (0.97, 1.08) 1-4 1 3 1,2
T13 85 1.04 (0.97, 1.11) 1-4 1 3 3
  1. aDays when all pollutants are in the lowest quartile.
  2. bTerminal nodes represent different types of days that can be described in terms of the pollutant quartiles.
  3. cEach day is in one and only one terminal node; the column sums to 4010.
  4. d P-values are associated with the null hypothesis that the risk ratio for the pollutant indicator is 1.0.