Laserfiche WebLink
Coal Quality Data Review for Colowyo Coal Company <br />9 <br />hole by hole basis as to include old and new coal quality values of adjacent <br />holes within the coal quality model. <br />3.2.2 Ash and Btu /lb Variance <br />As part of reviewing the relationships between data sets, HGC also reviewed <br />the variance between Ash and Btu /lb values. When adding regression lines <br />to data in ExceITm R values can be displayed. In this study, the R (or R- <br />squared) value is the measure of the variance of the Ash over variance of the <br />Btu /lb. R values approaching 1.0 indicate that the data is closely tied and <br />that the regression equation accurately reflects the data. <br />HGC used the R values to compare ash versus Btu /lb, see Table 3. The R <br />value is an indication of how well ash and Btu /lb correlate, thus providing a <br />measure of data quality. In most instances, dry basis R2 values of ash and <br />Btu /lb should be very close to 1.0. If this number is less than about 0.90, <br />• then the one could assume that some data points are wrong (typographical <br />errors) or that some the samples have been oxidized. <br />Table 3 <br />Comparison Dry basis and As- received basis <br />Ash versus Btu/11b R2 Values <br />• <br />Company <br />Dry Basis <br />As- Received Basis <br />% Difference <br />KEC <br />.9975 <br />.9735 <br />2% <br />Utah <br />.9872 <br />.8965 <br />9% <br />Grace <br />.9245 <br />.6615 <br />28% <br />Table 3 illustrates that on a dry basis, the KEC and Utah drill hole data clean <br />and is probably reliable data. The Grace drill hole data might be reflecting <br />some minor oxidation of the samples, but n enough to excluding these data <br />from the modeling database. <br />July 2004 <br />Page 10 of 16 <br />