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2011 Assessment of the BRB -1 for Compliance with Phase Ill Performance Standards <br />COVER <br />As described above, in 2011, sample adequacy based on all -hit values was achieved for BRB -1 and each of <br />the reference areas except the Mountain Brush Reference Area. Thus, in consideration of the lack of a <br />sample size sufficient to detect a 10 percent reduction in the mean with 90 percent confidence (i.e. sample <br />adequacy), the upper limit of the possible values of the true mean (with a sample size of 18) was <br />determined. This can be done in either of two ways. <br />1) Confidence Intervals <br />15.0 <br />C.I. = — =t = *1.740 =6.15 <br />43.89 -6.15 =50.04 <br />2) Sample Adequacy Expression <br />s't <br />N = <br />d'' <br />d= <br />= 0.140 <br />15.0 * 1.740 <br />43.89 <br />. +d= 43.89 + (43.89 ; 0.140) = 50.04 <br />50.04 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 calculations, two - tailed t values with n -1 degrees of freedom are used. We are <br />concerning ourselves with the full range of possible values for mean, thus bi- directional concerns are <br />evident. From the CDRMS point of view, this pushes the limits out further and produces the highest <br />maximum value for the mean (at 90% confidence).] <br />24 <br />