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S the formula and nmin was calculated. The actual number of samples col- <br />lected (n) was then compared with nmin. If n nmin, then an adequate <br />number of samples had been collected and sampling for that parameter was <br />discontinued. If nF nmin, additional samples were collected, mean and <br />standard deviation were recomputed and the calculation was redone. <br />Sampling continued until n was at least equal to nmin. <br />Reference areas were considered comparable to the mine plan areas if they <br />did not have statistically significantly lower mean values of the measured <br />parameters of herbaceous cover and productivity. If levels measured on <br />the reference areas were equal to or greater than those found on the mine <br />area, this was satisfactory. <br />When reference areas showed lower mean values, the following statistical <br />formula was used to test whether the means were significantly different. <br />}E1 - Nc2 f t(.05, nI + nZ-2) SlZ + S2z <br />nl n2 where <br />x= mean values of two means being compared <br />t =the onetailed tabular tvalue at the 95$ <br />confidence level with appropriate degrees <br />of freedom (nl +.n2_2) <br />S3 =the variance of each sample <br />n =the number of observations in each sample <br />If the absolute value of the difference between the two means was greater <br />than the value computed from the formula on the right side of the page, <br />then the means were considered significantly different at the 95$ con- <br />fidence level. <br />3.0 RESULTS <br />3.1 Plant Species <br />A total of 84 plant species were encountered during the study; Table 1 <br />lists scientific and common names of these plants. Except for very common <br />_ species were easily identified, other species were collected and submitted <br />to Dr. Barry C. Johnston of Lakewood, Colorado, for expert identification. <br />Dr. Johnston is an expert on Colorado plants, with a special interest in <br /> <br />