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where: <br />n = minimum sample size <br />s = Sample variance (n -1 degrees of freedom) <br />d = Precision (0.10 for cover and production; 0.15 for <br />woody plant density) <br />x = Sample arithmetic mean <br />t = The (a =.10) t -table value for a 1 tail t -test, n -1 degrees of <br />freedom (infinite degrees of freedom may be used if n >30) <br />see Rohlf and Sokal 1969 <br />n = Sample size <br />All such calculations were based on data from a minimum of fifteen samples <br />NOTES ON THE COMPARISON OF DATA TO APPLICABLE REFERENCE AREA STANDARDS <br />Upon the formal comparison of cover data from reclaimed areas to applicable performance <br />standards, observed total all -hit herbaceous cover percentage must be adjusted for excessive <br />contribution by annual / biennial species (CDMG 1995, Guidelines Regarding Selected Coal Mine <br />Bond Release Issues, 1 (IV)A(4)). Herbaceous cover values used in such comparisons also must <br />exclude values for species present on the Routt County Prohibited or Restricted Noxious list or <br />that are listed as noxious by the State of Colorado (Colorado Dept. of Agriculture, Division of <br />Plant Industry, Title 35, Article 5.5, 101 -119, Lists A and B of Rules as replaced 2003). <br />For purposes of assessment of reclamation adequacy, all -hit herbaceous cover data from <br />reference area sampling is used as per Sage Creek Mine permit provisions. <br />It is also to be noted that the data from the two reference areas is weighted in accordance with <br />the original relative abundance of the types in the pre- mining landscape (83% mountain brush, <br />17% sagebrush /snowberry). In the process of weighting, a reliable estimate of variance is lost. <br />Thus the reference area standard is thereafter in the process treated as a technical standard (i.e. <br />without confidence limits) and one - sample t- testing is used. <br />5 <br />