Laserfiche WebLink
2012 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 18) was determined. This can be done in either of two ways. <br />1) Confidence Intervals <br />s 4.80 <br />C.1. = — *t = :1.740 =1.97 <br />vrt V18 <br />8.72 — 1.97 = 10.69 <br />N — <br />= 0.2;58 <br />2) Sample Adequacy Expression <br />4,30 *1.740 <br />3.72 * 18 <br />7+ = 3.72+ (3.72 ,K 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 />