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<br />• <br />STATE OF COLORADO RIC Nngn ~M. Gov crnm <br />DEPARTMENT OF NATURAL RESOURCES <br />D. Monte Pascoe, Executive Director <br />MINED LAND RECLAMATION <br />423 Centennial Builtling, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (303) 839-3567 <br />July 27, 1981 <br />III IIIlllllllllllll <br />David C. Shelton <br />Director <br />TO: Brian Munson <br />FROM: M.S. Savage <br />RE: N-G Vegetation/Sampling Adequacy <br />D. Duba's Correspondence of 7/17/81 and 7/20/81 <br />File No. C-003-80 ~~ <br />Brian , <br />Dave Duba has submitted information addressing the specific levels of confidence <br />achieved during vegetative sampling for each community and parameter. In <br />addition, he has submitted an F-test analysis for parameters which were found <br />to be below acceptable confidence levels. Mr. Duba's (and Mr. Botts) argument <br />is that if an F-test determines that the variances are not significantly <br />different between two samples, one can utilize a students t-test to determine <br />if there is a significant difference between the means of the samples. It is <br />my contention (as well as that of Larry Larson, staff statistician for OSM) that <br />a positive F-test determination does not necessarily indicate that a students <br />t-test may be justified. The F-test tests the variances of two samples and <br />determines if the samples are from the same population. We do not wish this <br />information. Rather, we wish to determine if the sample means of two different <br />populations are significantly different from each other. Additionally, we <br />must have accurate estimates of each population parameter. By analogy: If <br />carpenters built your home utilizing measuring devices to the nearest 1 meter, <br />would one be justified in trying to estimate the area of the floor plan in <br />square centimeters? <br />I have determined, with the aid of the materials just received, that R-G <br />should re-sample the following community parameters: <br />A. Aspen community <br />1. Reference area productivity and woody plant density** <br />2. Pre-mine productivity and woody plant density <br />B. Sagebrush community <br />1. Pre-mine productivity, cover, and woody plant density <br />2. Reference area cover. <br />C. Oak community <br />1. Pre-mine woody plant density <br />2. Reference area woody plant density** <br />