Laserfiche WebLink
t = 0.1 x X) n <br />• s <br />With R = mean <br />s = standard deviation <br />' n = number of samples <br />This is equivalent to the formula suggested by Mike Savage in his letter to <br />David Duba, dated July 14, 1981 (see attached copy). The 0.1 factor in the <br />equation implies estimation to within 10% of the actual mean value. Tabu- <br />lar t - values were from the p = 0.2 level fora two-tailed distribution, <br />with the appropriate degrees of freedom, providing 80% statistical confi- <br />dence in the estimate. For each data set, after some data were collected, <br />R, s, and t were computed. If the computed t did not exceed the tabular t, <br />sampling was continued and t was recomputed. This process was repeated <br />until the computed t exceeded the tabular t. At this point, sampling was <br />considered sufficient, as the data set estimated within 10% of the actual <br />mean value with 80~ statistical confidence. <br />• For data collected in 1981, the same sequence of data presentation will be <br />followed as for data collected and presented in the 1980 report. Table A.1 <br />and A.2 contains herbaceous biomass data collected in 1981 in the aspen <br />mine and reference areas. Thirty lmz plots were clipped on the mine area, <br />and 28 on the reference area. The mean dry weight on the reference area <br />(120.6 g/m2) slightly exceeded that on the mine area (112.3 g/m2). Clipped <br />samples were sorted into grass and forb categories; according to Mike <br />Savage, separation by species was not required, since cover data had been <br />previously presented by species in the 1980 report (personal communication <br />at Hayden Gulch mine, August 18, 1981). Grass and forb percentages were <br />comparable on the mine and reference areas, at 61% and 54~ respectively, of <br />the total, while fortis comprised the remainder. <br />Table A.5 presents shrub and tree density data for the aspen vegetation <br />type, for both mine and reference areas. The table includes data collected <br />in 1980 and three transects sampled in 1981 (nos. 5-7) for shrubs and ane <br />for trees in the mine area. Mhen combined with the 1980 mine area data, <br />• the 1981 data allow sample adequacy requirements to be met. The mean <br />density of shrubs and seedlings was 108.0 ± 6.4 per 250mz. <br />637C3 ' <br />