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considers field bindweed a species recommended for weed control but not mandatory control. Based <br />on the sampling results, the plant community on the reclaimed area achieved the approved species <br />diversity standard. <br />Due to the presence of field bindweed, the Division calculated vegetative cover success excluding the <br />contribution of field bindweed from the cover data. Vegetative cover excluding the contribution of <br />field bindweed equals 36.13%. This value is less than 90% of the 41 % cover standard (36.9%). As <br />stated in the Colorado Division of Minerals and Geology S3uid .lin . R .garding,G I ..t -d .oal Mine <br />Bond R .I .ac . Icc ~ .c dated April 18, 1995, an operator may employ hypothesis testing to <br />demonstrate that the difference (in this case 36.13% vs 36.9%) is not statistically significant. For <br />technical standards comparisons, one-sample hypothesis tests are appropriate statistical tests of <br />revegetation success. <br />The null hypothesis being tested is that the bond release block mean (u) is greater than or equal to <br />90% of the standard {Q) and can be stated as: H°: u ? Q <br />Using the one-sample t-test, if the calculated tc value is less than or equal to table t~ value, then H° is <br />not rejected and the reclamation would be still be considered successful. <br />From page 22 of the guideline, for the T-test formula. <br />t test: t~ = Q-X <br />Q = 90% of the standard <br />x =Bond release sample block mean <br /> =Standard error of the mean (s~~ ) <br />s =standard deviation <br />n =sample size <br />t° = calculated t value <br />Table value for tc = 1.345. n-1 degrees of freedom for alpha error probability of 0.10. <br />r - 36.9-36.13 = 0.2655 <br />` 10.86 <br />14 <br />Therefore 0.2655 < 1.345 (tc < t,) so the null hypothesis (H°) is not rejected, and revegetation is <br />deemed successful for cover when field bindweed data is excluded from the calculations to determine <br />the vegetation cover mean. <br />If you have any questions about the data or the process in general, please contact me. <br />Since y, /~ <br />Ke A. Gorham <br />Environmental Protection Specialist II <br />