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nmin = (t 2s 2 ) / (0.1 X )2 <br />where: n = the number of actual samples collected (initial size = 15 or 36) <br />t = the value from the one - tailed t distribution for 90% confidence with n -1 <br />degrees of freedom; <br />S 2 = the variance of the estimate as calculated from the initial samples; <br />x = the mean of the estimate as calculated from the initial samples. <br />If the initial samples do not provide a suitable estimate of the mean (i.e., the inequality is false), <br />additional samples would be collected until the inequality (n, <_ n) becomes true. <br />2.4 Success Evaluation <br />Success evaluations involve a direct (and perhaps statistical test) comparison of appropriate <br />parameters for each variable of interest. In the case of ground cover, comparisons are made against <br />reference area data of the same year. There are two methods in which reference area comparisons can <br />be made. The first is an absolute perennial cover comparison in which annual and biennial cover is <br />completely deleted from the vegetation cover data set. Implementation of this method requires noxious <br />weeds and annual and biennial cover be removed from the data set for the Phase II sampling area as <br />well as the two reference areas. Absolute perennial cover then becomes the only remaining data that <br />can then be used in a direct or statistical reference area comparison. <br />The second method uses guidance provided by the Colorado Department of Mining, Reclamation, <br />and Safety. These guidelines provide an opportunity for an allowable contribution of 10% relative cover <br />of annual and biennial cover to be used in the reference area comparison. Using this comparison <br />method, annual and biennial cover must then be included from the reference area. However, as with the <br />first method, implementation of this second procedure requires noxious weeds be removed from total <br />cover data set. Next, annual and biennial absolute cover must be converted into relative cover to <br />facilitate a determination of the 10% maximum. Annual and biennial cover exceeding 10% relative cover <br />can then be converted back to absolute cover to be deducted from the total remaining cover without <br />noxious weeds. The result of this calculation is perennial cover with the 10% allowable relative cover of <br />CEDAR CREEK ASSOCIATES, INC. Page 7 Colowyo Coal Co. Phase 11 Evaluation <br />