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2011 Assessment of BRB -5 for Compliance with Phase Ill Performance Standards <br />COVER <br />As described above, sample adequacy based on first -hit values was achieved for BRB -5 and the <br />Sagebrush Reference Area, but it was not for the Mountain Brush Reference Area. Thus, in consideration <br />of the lack of a sample size sufficient to detect a 10 percent reduction in the mean with 90 percent <br />confidence (i.e. sample adequacy), the upper limit of the possible values of the true mean (with a sample <br />size of 21) was determined. This can be done in either of two ways. <br />1) Confidence Intervals <br />s 9.15 <br />`.i, = — =t = „� .1,725 = 3.44 <br />20.95- 3.44 =24.39 <br />d. <br />s't' <br />d <br />= 0.1644 <br />2) Sample Adequacy Expression <br />9.15 *1.725 <br />20.95 21 <br />y” + d = 20.95 + (20.95 R 0.1644) = 24.39 <br />24.39 percent allowable herbaceous cover represents the highest possible value of the true mean for the <br />Mountain Brush Reference Area. <br />[Note in the above two - tailed t values with n -1 degrees of freedom are used. We are concerning <br />ourselves with the full range of possible values for mean, thus bi- directional concerns are evident. From <br />the CDRMS point of view this pushes the limits out further and produces the highest maximum value for <br />the mean (at 90% confidence). Also note that as sample size proceeds past the minimum (15) samples, <br />the upper confidence limit is likely to decline if only because n increases in the denominator of expression <br />1) above. Thus use of the upper confidence limit as the cover value for the Mountain Brush Reference <br />Area likewise takes the highest value forward into hypothesis testing and thus protects the interests of <br />CRDMS.] <br />19 <br />