Table 8 Test for independence in ultra-fine particles of green and residential area (winter, spring)

Classification			Levene's statistic		t-test for equality of means
			F	Sig.	t	af	Sig (2-tailed)	Mean difference	Std. error difference
Winter	Green	Equal variances assumed	0.512	0.475	1.774	254	0.077	4.328	2.440
		Equal variances not assumed			1.774	253.954	0.077	4.328	2.440
	Residential area	Equal variances assumed	0.147	0.702	2.622	254	0.009	6.148	2.345
		Equal variances not assumed			2.622	252.813	0.009	6.148	2.345
Spring	Green	Equal variances assumed	8.673	0.004	8.187	254	0.000	11.17188	1.36458
		Equal variances not assumed			8.187	236.060	0.000	11.17188	1.36458
	Residential area	Equal variances assumed	10.851	0.001	10.889	254	0.000	14.64063	1.34453
		Equal variances not assumed			10.889	231.205	0.000	14.64063	1.34453