Table 2.

T-test statistics for climatic variables for year of occurrence. The table shows the t-test statistics for climatic variables (in year of WNV disease occurrence) in census blocks with and without WNV disease incidence. All of the t-tests used 'equal variance not assumed' version of test in SPSS.

Variable	Year	Degrees of Freedom	With WNV Mean	Without WNV Mean	t-value	P
Precipitation	2002	54	768	763	-0.33	0.74
	2003	140	719	762	-5.63	<0.001
	2004	22	848	850	0.12	0.901
	2005	35	709	698	0.66	0.515
	2006	35	743	779	-2.9	0.006
Dewpoint	2002	54	4.35	4.4	0.50	0.62
	2003	140	3.16	3.42	-3.38	<0.001
	2004	22	4.61	4.33	-1.71	0.1
	2005	35	4.73	4.74	-0.10	0.922
	2006	35	4.86	5.01	-1.09	0.283
Max. Temp.	2002	54	15.7	15.7	-0.37	0.71
	2003	140	15.2	15.1	0.70	0.483
	2004	22	15.2	14.8	-1.86	0.076
	2005	35	15.7	15.8	-0.55	0.583
	2006	35	16.2	16.1	0.28	0.783
Min. Temp.	2002	54	3.71	3.82	0.66	0.52
	2003	143	2.73	3.09	-3.75	<0.001
	2004	23	3.17	3.68	-2.51	0.02
	2005	35	3.65	4.04	-2.74	0.01
	2006	35	4.29	4.55	-1.56	0.128