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. t = X A - X ER <br />S I P + S2 P <br />n A n ER <br />where <br />S 2 _ (n -1)S 2 A +(nER —1)S 2 ER <br />P <br />(nA -1) +(nER -1) <br />S2 = Sample variance (pooled) <br />xA = affected area mean <br />xR = reference area mean <br />t = two - tailed t -value with n -1 degrees of freedom <br />S2 = variance among affected area samples <br />S2 = variance among reference area samples <br />nA = number of affected area samples <br />nR = number of reference area samples <br />• The above calculated t value is compared to a two- tailed t value at 95 percent confidence (0.05 probability) <br />with appropriate degrees of freedom, as presented in a standard t value table. If the calculated value is less <br />than or equal to the tabular t value, the "comparability" of the reference and affected areas is deemed <br />acceptable. <br />Climatic Data <br />Seneca Coal Company (SCC) has historically provided precipitation data for the nearby Seneca II <br />and IIW Mines. These data were used to prepare the climate figures for these studies. Since the <br />long -term average for the Seneca IIW mine exists for only 25 years, the long -term average <br />monthly precipitation data from the NOAH administered Western Regional Climate Center <br />(WRCC) for the nearby town of Hayden (Station 053867) were used as an appropriate base for <br />comparison. SCC also provided temperature data for the nearby Seneca IIW Mine in 2008; <br />however, for temperature analysis for these studies, temperature data from the Hayden station <br />were used. <br />• 9 <br />