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Table 3 Comparisons of study samples and non-participants

From: Road traffic noise and children’s inattention

  Pregnancy sample   Postnatal sample  
Study sample Non-participants p-value Study sample Non-participants p-value
Average 5-y road traffic noise (SD), n     54.1 (7.4), n = 1384 55.1 (7.6), n = 4834 <.0001
Road traffic noise at age 8 (SD), n     53.1 (7.8), n = 1384 53.9 (8.2), n = 5484 .001
Road traffic noise, pregnancy (SD), n 55.8 (8.3), n = 1934 56.6 (8.4), n = 6425 .0001    
Average 5-y income (SD), n     992,139 (540759), n = 1384 901,693 (580480) n = 7579 <.0001
Income at age 8 (SD), n     1,046,052 (621477), n = 1384 948,394 (678449) n = 7719 <.0001
Income, pregnancy (SD), n 786,438 (573046), n = 1934 767,439 (587234), n = 9688 .19    
Mother’s education, n n = 1934 n = 10,036   n = 1384 n = 10,586  
  > 4 years univ./college 37.0 33.5 <.001 41.6 33.1 <.001
  ≤ 4 years univ./college 49.9 47.1   45.3 47.8  
 High school 13.1 19.4   13.1 19.1  
Ethnicity, % western, n 93.7, n = 1934 86.6, n = 10,148 <.001 91.3, n = 1384 87.3, n = 10,698 <.001
Gender, % boys, n 49.5, n = 1934 50.9, n = 10,206 .26 50.4, n = 1384 50.7, n = 10,756 .81
Maternal smoking, pregnancy, % yes 3.9, n = 1934 4.8n n = 8871 .12 4.2, n = 1384 4.7, n = 9421 .44
Maternal alcohol consumption, pregnancy, % yes 7.2, n = 1934 7.3, n = 7278 .98 9.5, n = 1384 6.9, n = 7828 <.001
% birth weight < 2500 g, n 2.8, n = 1934 3.2, n = 10,202 .33 3.5, n = 1384 3.1, n = 10,752 .37
% premature, n 4.3, n = 1934 4.7, n = 10,192 .39 4.5, n = 1384 4.7, n = 10,742 .73