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WESTERN - - - - <br /> RESOURCE - <br /> DEVELOPMENT - - <br /> CORP. <br /> P.O. Box 467 <br /> 711 walnut street.suite 200 <br /> Boulder,Colorado 80306 ' <br /> (am)449.-60M May 25, 1981 <br /> Mr. Douglas W. Bowman <br /> Environmental Coordinator <br /> Mid-Continent Resources, Inc. <br /> Box 158 <br /> Carbondale, CO 81623 <br /> Re: MLRB Adequacy. Review - Coal Basin Mines <br /> Dear Doug: <br /> This letter addresses agency review questions for vegetation. <br /> In our opinion and the opinion of recognized statistical <br /> �- ecologists at universities in Colorado and Wyoming, a one-tailed <br /> �. t-test is appropriate. We contacted Dr. Lymon McDonald, Univer- <br /> sity of Wyoming, and Dr. David Chiszar, University of Colorado, <br /> and presented the facts. Both these prominent statisticians <br /> agree that a one-tailed t-test is appropriate in the case under <br /> discussion. Furthermore, we contacted Mr. Jim Herron, MLRB, <br /> and he agreed that use of the one-tailed t-test was all right. <br /> The origin of the statistics used for sample adequacy is the <br /> standard error of the mean as a percent of the mean (dx_ / x) . <br /> The deviation of S2z2 <br /> nmin _2d2 <br /> is relatively simple and can be shown if MLRB is not familiar <br /> with it. Since the distribution of t has been used as the <br /> criterion for applying the sample adequacy formulas (by. virtually <br /> all agencies including MLRB) , let us examine the purpose for <br /> determining sample adequacy to find whether a one-tailed or two- <br /> tailed test is most appropriate. In Colorado, data collected <br /> from the reference area is to be compared to those from the <br /> reclaimed area. The regulations under which comparisons -are <br /> made (4.15.8, 4.15.9, 4.15.10) state that the particular <br /> parameter (cover, production, or stem density) in the reclaimed <br />