Table 3.

Multilevel models parameter estimates for ambient noise exposure and mathematics scores (n pupils = 586; n schools = 31)

	Model 6			Model 7			Model 8
	β	95 % CI	p	β	95 % CI	p	β	95 % CI	p
Independent variables
Intercept	69.83			53.87			56.89
Lden at home (for 1-dB increase)	−0.22	−0.53 to 0.09	0.07	−0.10	−0.40 to 0.20	0.50	−0.03	−0.32 to 0.26	0.85
LAeq,day at school (for 1-dB increase)	−0.53	−1.18 to 0.11	0.11	−0.55	−1.01 to −0.08	0.02	−0.44	−0.85 to −0.02	0.04
Sex
Female				Ref			Ref
Male				4.43	1.83 to 7.03	<10−3	5.19	2.67 to 7.72	<10−3
Age
≤8 years old							Ref
>8 years old							−10.83	−14.74 to −6.92	<10−3
Missing value							6.85	1.84 to 11.86
Mother’s education
Elementary school				Ref			Ref
Middle school				5.29	−3.91 to 14.49	<10−3	3.50	−5.43 to 12.44	<10−3
High school				9.60	0.60 to 18.60		6.26	−2.55 to 15.06
University				15.66	6.61 to 24.71		11.71	2.84 to 20.58
Missing value				3.21	−6.37 to 12.79		2.00	−7.31 to 11.30
Household socio-economic status
SES-1				Ref			Ref
SES-2				1.19	−3.64 to 6.01	0.15	2.09	−2.61 to 6.78	0.18
SES-3				1.16	−3.98 to 6.29		2.07	−2.92 to 7.05
SES-4				2.49	−2.52 to 7.51		3.50	−1.37 to 8.38
Missing value				−5.55	−12.34 to 1.24		−3.61	−10.25 to 3.03
Parents’ employment status
No full-time worker				Ref			Ref
At least one full-time worker				2.82	−0.45 to 6.10	0.14	2.77	−0.41 to 5.96	0.13
Missing value				7.97	−5.02 to 20.95		8.29	−4.30 to 20.87
Random parameters
Level 2: school	55.27	18.15		24.00	9.69		17.17	7.69
Level 1: pupil	266.08	15.97		241.07	14.46		227.50	13.64
Percentage of the explained variance	2.7			19.7			25.9

β = the estimated change in the Mathematics score; CI = confidence interval; p = p value; SES-1 =working class or unemployed; SES-2=non-managerial position/clerk; SES-3 = middle class job/mid-management position; SES-4 = senior management position/artisan, shopkeeper, and entrepreneur/corporate manager