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Table 3 T-test statistics for climatic variables for year preceding occurrence. The table shows the t-test statistics for climatic variables (from year preceding 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.

From: Landscape, demographic, entomological, and climatic associations with human disease incidence of West Nile virus in the state of Iowa, USA

Variable

WNV Occurrence Year

Degrees of Freedom

With WNV Mean

Without WNV Mean

t-value

P

Precipitation

2002

54

887

879

0.56

0.58

 

2003

145

693

767

-8.19

<0.001

 

2004

23

702

761

-4.27

<0.001

 

2005

35

819

848

-2.13

0.041

 

2006

35

712

698

0.74

0.464

Dewpoint

2002

54

4.83

4.87

-0.37

0.71

 

2003

140

3.97

4.43

-6.01

<0.001

 

2004

22

3.04

3.41

-2.22

0.037

 

2005

35

4.29

4.61

-2.36

0.024

 

2006

35

4.71

4.74

-0.23

0.818

Max. Temp.

2002

54

15.4

15.3

-0.57

0.57

 

2003

140

15.7

15.7

0.31

0.76

 

2004

22

14.8

15.1

-1.88

0.074

 

2005

35

15.1

15.2

-0.68

0.5

 

2006

35

15.8

15.8

0.07

0.94

Min. Temp.

2002

54

3.93

4.02

-0.57

0.57

 

2003

143

3.32

3.84

-5.48

<0.001

 

2004

23

2.58

3.07

-2.47

0.021

 

2005

35

3.18

3.68

-2.97

0.005

 

2006

35

3.77

4.04

-1.48

0.147