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Using regression analysis, the following equation was developed to describe the relationship <br />between dissolved Zinc at A-72 as a function of stream flow vrd whether or not the samples <br />were taken on the rising limb of the hydrograph (referred to as the "Rise"). <br />In(Zn~_~z) = 8.30 - 0.462 * In(flow) + 0.687 Rise (i) <br /> <br />Where: <br />Statistical t-tests are performed to determine whether the two independent vaziables <br />(In(flow) and rise) are important predictors of dissolved zinc. The results are shown in <br />Table A-2. A slope coefficient for each of the variables in the equation is shown under <br />"Coef' in the table. The value of the intercept, or constant in the equation is also shown. <br />At the bottom of the table the adjusted correlation coefficient ("R-Sq(adj)") is presented. <br />An R-Sq(adj}value of 84.4 °lo means that 84 percent of the variability in dissolved zinc <br />concentration at A-72 is accounted for by the In(flow) at A-72 and whether or not the <br />sampled occurred during the rising limb of the hydrograph. Also at the bottom of the <br />table is the standazd error "S", in this case 0.1532. The standard error is a measure, <br />which indicates the spread of the points azound the fitted line of regression. <br />The column to the far right contains P values for each test. The P value is a measure of <br />the believability of the hypothesis that no effect on Y (the ln(Zn)) is caused by that X (the <br />]n(flow)). A small value for P, traditionally considered as smaller than 0.05 (5%), is <br />evidence that the X variab]e does affect the values for Y. A P value smaller than 0.05 for <br />Rise indicates that there are differences in zinc concentrations if the samples are taken in <br />the rising limb of the hydrograph. The actual P value for the Rise is 0.000. <br />Table A-2. Regression Results for the Zinc Concentration at A-72 <br />The regression equation is <br /> ln(ZnA_~Z) = 8.30 - 0.462 hi(flow) + 0.687 rise <br />Predictor Coef St Dev T P <br />Constant 8.2997 0.2435 34.08 0.000 <br />ln(flovt~) -0.46175 0.04910 -9.40 0.000 <br />Rise 0.6872 0.1042 6.59 0.000 <br />S = 0.1532 R-Sq = 86.4% R-Sq(adj) = 84.4% <br />Appendix A <br />ln(ZnA_~2) =the natural logarithm of predicted dissolved zinc concentration <br />(in ug/L) at A-72 <br />In(flow) =natural logarithm of stream flow (in cfs) at A-72 <br />Rise = I if the flow is taken during the rising limb of the hydrograph and <br />0 if it is not <br />ZnA-~z = the predicted dissolved zinc concentration (in ug/L) at A-72 <br />e =base of the natural logaritlun <br />232565 <br />