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REVIEW QUESTION <br />4.15.7 <br />(3)(b) A statistical comparison between the mine and reference areas <br />is necessary regardless of which values (mine or reference area) are <br />higher for vegetative sampling. There are also some questions about <br />the statistical analysis of the reference areas. Please see enclosed <br />memo from Mike Savage. <br />AGC Dl1NCF <br />Results from the reference areas study (Appendix G) are summarized <br />for biomass, cover and woody plant density measurements. Sample <br />adequacy is addressed in terms of minimum sample number and confi- <br />dence levels for all data sets in reference areas and future mining <br />disturbance areas. Results of t-test comparisons between mine and <br />reference areas are presented for the measured parameters. <br /> <br />Since all communities of interest at the Hayden Gulch mine were <br />dominated by woody vegetation, the required level of sampling was <br />to estimate within 10% of the actual mean value with 80% statistical <br />confidence. Sample adequacy for each data set was assessed in terms <br />of the minimum number of samples required (nmin) and the confidence <br />level achieved based on a computation of t. These were done using <br />a one-tailed t-test to see if the available data estimated within <br />10% of the population mean value with 80q statistical confidence. <br />The formulas used to calculate nmin and t were: <br />n- 2 (s x 0.84) 2 t o (d x) 2 <br />run (d x x) 2 s2 <br />• <br />