Laserfiche WebLink
Within each sampling unit, each vegetation parameter was sampled suf- <br />• ficiently to estimate within 10$ of the actual mean value with 80$ statistical <br />confidence. Since all communities were dominated by woody vegetation, <br />these sampling intensity guidelines were used, as recommended by the <br />CMLRB. <br />The following formula was used to test whether adegate sampling had been <br />achieved for each parameter: <br />n . <br />rmn = 2(s x 1.28)2 <br />0.2 x x 2 <br />where <br />nmin = minimum number of samples to achieve adequacy <br />s =standard deviation of the data set <br />1.28 =one tailed tvalue with infinite degrees of freedom <br />at p = 0.1 (90$ confidence level) <br />0.2 =degree of confidence desired in detecting reduction <br />in the mean (80$ confidence) <br />and x =the sample mean. <br />This sample adequacy formula was taken from guidelines for sampling <br />vegetation established by the Wyoming Departmart of Environmental Quality <br />(1979). It is similar to the formula proposed by Larson (1980), but gives <br />a slightly more conservative (higher) nmin value than his formula: <br />where: <br />n t2 s2 <br />aun = <br />d2 <br />and <br />where: <br />t2 = (1.28) 2 (at the 90$ confidence level, one-tailed value) <br />s= =variance of the data set <br />d2 =the degree of confidence desired in the estimate <br />(at 80$ confidence, d2 = (0,2 x x)2). <br />• After a certain amount of data had been collected for each parameter, the <br />mean and standard deviation were computed. The numbers were placed in <br />