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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.

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

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