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Rule 2.04-10. When adequate sample parameters have been obtained for cover, production, and density, [hey will be combined and weighted for each revegetation type and for [he corresponding reference area. This is • accomplished by weighting each individual x and s? relative to their respective acreages, and [hen combining [Ire weighted means and variances into one value (for each variable) for the entire area under consideration for bond release. These weighted values will be determined as follows: k Ai X I x = t=1 we k E Ai i=1 k k s2/n = ~ (Ai / E Ai)2 (s? /ni) we i=1 i=l where: _ x = weighted mean we s2/n = weighted variance we k = total number of revegetated types under consideration far bond release • Ai = premining acreage (for reference area data) or postmining acreage (for revegetated type data) for the ith revegetated type or corresponding reference area. Once these parameters are obtained for each variable the means can be quickly checked arithmetically to determine if the revegetated area's variables are high enough or whether a t test must be performed. The arithmetic check requires a determination of the status of the following inequality for all variables: x - C xwerf?0 where: x werv = estimated weighted mean for cover, production, or density taken from the revegetated areas under consideration for bond release. x werf = estimated weighted mean for cover, production, or density from the corresponding reference areas. C = allowable reduction from the reference area standard and in this situation equals 0.9. If [Iris inequality falls for any given variable, then the following steps will be taken for that variable, otherwise the test Itas been passed. The sample t statistic (tcalc) is determined as follows: kale = (swerv - C xwerf)/ sxwerv -xwerf • where: _ _ sxwerv -xwerf = ~ s2p ((°werv + ~~werf)/°werv ~t~~erf)) SIR 97-I>J 1.05-I 16 Revised 12/10/97