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<br />xi-x2 <br />where C100) = change in <br />x1 expressed <br />t,20 = two-taile <br />percent <br />degrees <br />the mean, xi, <br />as percent, <br />~ °t" value at 20 <br />confidence for (n-1) <br />of freedom, <br />s2 = variance of the sample mean; <br />n number of samples; and <br />x sample mean. <br />For the vegetation cover data for this study: <br />1/2 <br />reliability = (100> <br />2s2 <br />t.20 n <br />x <br />r~ <br />L <br />1/2 <br />2(9.04)2 <br />1.32 20 <br />(100) <br />69.5 <br />. ~ <br />I! <br />This calculation shows sampling intensity adequate to detect <br />a five percent deviation from the sample mean with eighty <br />percent confidence. ' <br />Adequate sample size is calculated so that statistical <br />comparisons can be made. The number of samples needed to <br />achieve sample adequacy is a function of the variance and <br />the square of the mean, given by: <br />number of samples <br />n = to achieve <br />sample adequacy <br />82 <br />Ct.20>2 (2s2) <br />_ <br />IC0.1) (x)7 <br />Revised 5/87 <br />