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Mr. Ross Gubka, P.E. <br />Western Fuels-Colorado <br />December 11, 2007 <br />Page 6 <br />and list species (by scientific and common name), with absolute and relative <br />mean cover by species and life form, as well as means for total plant cover, <br />total desirable plant cover, and total cover for bare ground, litter, and rock. <br />The production table should present mean production in pounds per acre by <br />life form category and for total plant production and total desirable plant <br />production. <br />11. We believe a number of clarifications are warranted with respect to details <br />included within the "Revegetation Success Criteria and Statistical Procedures- <br />Irrigated Pasture" section, beginning on page (e)-35. <br />a) The next to last sentence on page (e)-35 indicates that a minimum of 30 sample <br />observations _aa be required if sample adequacy is not achieved. In fact, if <br />sample adequacy is not achieved, a minimum of 30 sample observations is <br />required to demonstrate success. Please revise the sentence as appropriate. <br />b) The last sentence of the Case 3 paragraph on page (e)-37 indicates that the t- <br />test shown on page (e)-36 would be used in the situation described. This is not <br />correct; the t-test on page (e)-36 is applicable to the "standard null" formulation <br />rather than the "reverse null" formulation. The one-sided t-test listed in Rule <br />4.15.11(2)(c) should be employed in this situation. In this test, the numerator <br />parameters from the test shown on page (e)-36 are reversed. Please amend the <br />sentence to clarify the correct t-test to. be used. <br />c) The discussion and statistics given in the paragraph applicable to Case 4, <br />beginning on page (e)-37, contain some errors and omissions. We recommend <br />that the narrative paragraph on page (e)-37 be amended to state: <br />4) Ifsample adequacy is not achieved in the reference area <br />(regardless of whether sample adequacy is achieved in the <br />reclaimed area), success will be demonstrated by use of the two- <br />sample "reverse null" t-test with Satterthwaite approximation of <br />standard error and degrees of freedom. The test can be used if the <br />following 2 conditions are met: 1) a minimum of 30 sample <br />observations are taken in the reclaimed area and also in the <br />reference area, and 2) the reclaimed area sample mean is greater <br />than Q. <br />For clarification, we recommend that the "acceptancetrejection rule" for the Nest <br />be included immediately following the Nest on page (e)-38: <br />If the calculated t value is greater than the table t value (alpha = <br />0.20, dfsAT), then the null hypothesis is rejected. <br />Please consider these recommendations and revise the section as appropriate.