2001-12-11_PERMIT FILE - C1981010A (7)

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i Subtleties Of Statistical Comparisons Because the Curren[ regulatory procedures for evaluating revegetation suc- cess rely heavily on statistics, it is also important to understand the real effects of statistical analyses. For example, although a single-tailed t test will minimize the sample size required and. reduce sampling costs, i[ will result in increasing the stringency of the test of success. In other words; it will result in disproving success sooner than will a two-tailed analysis. Another point to be realized is [hat although the 80: confidence level speci- fied for testing for shrublands intuitively seems less stringent than a 90% test, i[ is in fact more stringent. For example, one may be 90% certain the true mean occurs between 8 and 12, but only 80% certain it falls between 9 and 11. In this case, an estimate of the mean equal to 8.5 could not 6e rejected as falling outside the expected bounds of estimating error with 90% confidence, but could be rejected with 80% confidence. mplifyino the Solution Si • _ Probably our most difficult problem to overcame in developing an efficient and effective system for proving success of revegetation on mined lands is the professional biases we hold from traditional ways of doing things. Traditional ways of evaluating vegetation were never intended to demonstrate success or failure of reclaimed lands. They were developed instead to be mana gement tools to indicate animal carrying capac ities and the influence of animal use on range condition and trend largely by a trial and error process. Certainly some objective and quantifiable standard for testing success is necessary to protect operators and regulatory authorities alike. Current regu- latory approaches, however, require detailed and intensive ecological studies of reclaimed sites without recognition of the problems associated with collect- 1 it i ~. -10- 4 -'