Laserfiche WebLink
Perennial Grass <br />Annual Grass <br />Sub -shrubs <br />Perennial Forb <br />Annual Forb <br />Noxious Weeds (if found) <br />All production samples were returned to the lab for drying and weighing. Drying was conducted at 105° <br />C until a stable weight was achieved (24 hours). Samples were then re -weighed to the nearest 0.1 gram. <br />2.5 Sample Adequacy Determination <br />Sampling within each managerial unit was conducted to a minimum of 30 or 43 cover or production <br />samples per unit (Rule 4.15.11(2)). From these preliminary efforts, sample means and standard <br />deviations for total non -overlapping vegetation ground cover and production were calculated. For bond <br />release applications, the typical procedure is that sampling must continue until an adequate sample, nmi,, <br />has been collected in accordance with the Cochran formula (below) for determining sample adequacy, <br />whereby the population is estimated to within 10% of the true mean (N) with 90% confidence. <br />When the inequality (nn,i„ <_ n) is true, sampling is deemed adequate; and nmi„ is determined as <br />follows: <br />nmin = (r2s2) I (0.1 X )2 <br />where: n = the number of actual samples collected (initial size = 30 or 43) <br />t = the value from the one -tailed t distribution for 90% confidence with n-1 <br />degrees of freedom; <br />s2 = the variance of the estimate as calculated from the initial samples; <br />x = the mean of the estimate as calculated from the initial samples. <br />If the initial samples do not provide a suitable estimate of the mean (i.e., the inequality is false), <br />additional samples would be collected until the inequality (nmin 5 n) becomes true. <br />July 2015 Page 13 <br />