2012-04-02_REPORT - C1994082 (7)

Home Browse Search

Statistical Methods STATISTICAL DESIGN Cover and herbaceous production data were collected in the interim sampling areas (2007 reclaimed areas) as were woody plant density data. No woody plant samples were placed in any of the reference areas. Sampling proceeded using a single stage statistical design. Sample locations in reclaimed areas were randomly plotted by use of an internal script routine within ArcView 9.3 software. Minimum spacing between sample points was 170 feet (one 50 m transect length). The SCC- assigned number of samples for a given parameter in a given area reflected previously experienced sample variability or the level of precision required for that area. In the extended reference areas, each reference unit was gridded and numbered. Grid cell size was 200 feet X 200 feet. These grid cells were placed contiguously by hand on maps of 1:4,800 scale. Sample locations were selected as the center points of grid cells selected using random numbers generated by computer. Sample points were located in the field using topographic maps. Cover and woody plant density transects were located and oriented using a blind throw of a meter stick. The final location of each herbaceous production plot was chosen with a blind throw of the sampling hoop made from the origin of the associated cover /woody plant density transect. At each cover /woody plant density sampling location, the slope (percent) and aspect of the site were determined and recorded, as was the orientation of the transect (in degrees not corrected for magnetic declination). SAMPLE ADEQUACY CALCULATIONS Sample adequacy calculations for parameter estimation without hypothesis testing were carried out using the formula as prescribed by the Colorado Mined Land Reclamation Board for parameter estimation without hypothesis testing (CDMG 1995): N min a t 2 s 2 (d x )2 where: = one - tailed t -value with (n -1) degrees of freedom, a =0.10 4