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fr~ <br />For the two-stage sampling of shrub density, calculation of sample variance for use in the above <br />sample adequacy formula was as follows (expression 10.10 of Cochran 1963): <br />1 -f 1 1-fp <br />Vy = S12 + S22 <br />n mn <br />where: <br />Vy =Overall variance of shrub density data <br />f1 = n/N <br />fp = m/M <br />S12 = variance among primary unit means <br />• Sp2 = variance among elements within primary units relative to the primaryunit means <br />N =total number of primary units that exist (and are to be potentially sampled) <br />n =number of primary units actually sampled <br />M =total number of sample elements that which exist within each primary unit <br />m =number of primary unit elements actually sampled in each primary unit <br />Confidence limits for comparisons to reference areas were calculated using the formula for <br />Post-mining Comparisons on page 17 of CMLRB (1988), using an estimated t-value of 1.65. <br />Confidence limits far areas not being compared to a reference area (i.e. shrub density), were <br />calculated as 1.65 standard errors of the mean, i.e.: <br />U <br />9 <br />