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Revegetated area is at least 90% of the herbaceous cover and productivity on the reference azea with 90% statistical <br />confidence. If herbaceous cover and productivity on the revegetated area is less than the weighted cover and <br />• productivity on the reference areas, aone-tailed "t" test will be performed to determine if there is a statistically <br />significant difference. <br />Pursuant to Rule 4.15.8, Colorado Yampa 'Coal Company is proposing the following standard to demonstrate <br />species diversity has been achieved on the reclaimed areas. The species diversity standard will be met when alfalfa <br />does not exceed 75% relative production, perennial grasses shall provide at least 25% relative production and no <br />single species shall exceed 75% relative cover. <br />Revegetation success has been met when the calculated "t" is equal to or less than the "t" value from the one-tail "t" <br />distribution table. <br />The formula to be used is given on page 13 of "Draft: A Statistical Evaluation on Coal Lands in the West", L.L. <br />Larson, OSM, Region V, February 26, 1980. The formula reads: <br />xi-xz <br />4= <br />x, <br />xz <br />sit <br />sz2 <br />n, <br />nz <br />U <br />2 2 <br />si + sz <br />n, nz <br />=calculated estimate of t value <br />=mean for reference area data <br />=mean for revegetated azea data <br />=variance of referenced azea data <br />=variance of revegetated area data <br />= number of observations of reference area data set <br />= number of observations of revegetated area data set <br />TR 98-09 2.05-9I l l!?0198 <br />