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2012 Assessment of BRB -5 for Compliance with Phase 111 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 18) was determined. This can be done in either of two ways. <br />1) Confidence Intervals <br />s 4.So <br />C.1. = =t = 18 = 1.740 = 1.97 <br />8.72-x-1.97 =10.69 <br />2) Sample Adequacy Expression <br />s2t2 <br />N =;i= <br />fx- 2t2 4.802 :1.7402 <br />d= _ <br />2 N 8.722 x.18 <br />= 0.2258 <br />x +d= 8.72 +(8.72 *0.2258) =10.69 <br />10.69 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).] <br />Calculation of 90 percent of the cover performance standard appropriate for 2012 sampling using the <br />highest possible value for the Mountain Brush Reference Area component is demonstrated below. <br />25 <br />