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• t2s2 <br />nm = <br />(d-x y <br />where: <br />nm = minimum sample size <br />s2 = 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 (or.10) t-table value for a 1 tail t-test, n-1 degrees of <br />freedom (infinite degrees of freedom may be used if <br />n>30) <br />n =Sample size <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 first-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, first-hit herbaceous cover data from <br />reference area sampling are DOUBLED as per Seneca 11 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). It was necessary to sample each to adequacy (see below) but in the <br />process of weighting, a reliable estimate of variance is lost. Thus the reference area standard is <br />thereafter in the process treated as a technical standard (i.e. without confidence limits) and one- <br />sample Westing is used. <br />5