Statistical Tools for Air Pollution Assessment: Multivariate and Spatial Analysis Studies in the Madrid Region

Table 3

Pearson’s correlation coefficients matrix among the four air pollutants (top). The sample size is given in brackets, and the p value is given in italic.

	NO	NO2	PM10	O3
NO	—	0.9442	0.6314	−0.8182
	—	(22)	(22)	(22)
	—	≤0.0001	0.0016	≤0.0001
NO2	0.9442	—	0.5404	−0.8928
	(22)	—	(22)	(22)
	≤0.0001	—	0.0094	≤0.0001
PM10	0.6314	0.5404	—	−0.7296
	(22)	(22)	—	(22)
	0.0016	0.0094	—	≤0.0001
O3	−0.8182	−0.8928	−0.7296	—
	(22)	(22)	(22)	—
	≤0.0001	≤0.0001	≤0.0001	—