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where: <br />• to = calculated estimate of t value <br />X1 = mean far reference area data (cover or production) <br />X2 = mean for revegetated area data (cover or production) <br />2 <br />sl = variance of reference area data <br />2 <br />s2 = variance of revegetated area data <br />nl = number of observations of reference area data set <br />n2 = number of observations of revegetated area data set <br />'Ihe approved shrub density standani for rangelard is 1000 stems per acre, Zhe <br />species diversity starrL*-~ for rangeland states that at least 4 species will make <br />up 64$ of the relative percent composition in the reclaimed plant ~~~*+~ty aid <br />no single species will contribute more than 40$ of the relative ooe~osition. Rhe <br />species diversity starrl?**j far pastureland states that no single species shall <br />exceed 75 percent relative production and perennial grass shall provide at least <br />25 percent relative production. Also, no single species shall exceed 75 percent <br />• relative Dover. <br />Field sampling will meet a statistical m~*+~+~'"' of 90$ confidence with 10$ <br />precision. Adequacy of sample size will be deteYmined using the following <br />formula (USDI, Bureau of Iard Management Manual 4412-Physical Resource Studies, <br />August 10, 1979): <br />m = r t s 1 <br />I\ p x <br />Where: <br />rjp = Miniman amber of trailSectS necessary to sample within the <br />ps~escribed precision and confidence <br />t = A value fran the "t" distribution table which establishes the level <br />of confidence; t = 1.645 for 90$ confidence; <br />s = 5~.+Awr.9 deviation calculated as: <br />• S = X-X = <br />n-1 <br />Where: X = tlansect mean <br />MR 91-68 780-137 (a) Revised 06/11/91 <br />