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APPENDIX A <br /> SEN'S SLOPE AND MANN-KENDALL TREND ANALYSIS METHODS <br /> Sen's Slope analysis is a simple non-parametric procedure with measures the change in <br /> constituent concentrations per unit time. Sen's method is not greatly affected by outliers, and the <br /> slope can be computed when data are missing. Sen's estimator is closely related to the Mann- <br /> Kendall test,which is a non-parametric rank correlation test for trend. <br /> The Mann-Kendall test for trend uses only the relative magnitudes of the data rather than their <br /> actual values,therefore, missing values are allowed, and constituents that are reported as less <br /> than the detection limit can be used by assigning values equal to half the detection limit. The <br /> Mann-Kendall test is recommended in"An Evaluation of Trend Detection Techniques for use in <br /> Water Quality Monitoring Programs,"Jim C. Loftis, et al. (USEPA), 1989. <br /> Both the Sen's Slope and Mann-Kendall tests are discussed further in"Statistical Methods for <br /> Environmental Pollution Monitoring,"Richard O. Gilbert,Van Nostranc,New York, 1987. <br /> For the Harney Lane Sanitary Landfill,the null hypothesis is"no statistically significant trend <br /> constituent concentrations exist." The null hypothesis is rejected if trends in the data are <br /> significant at alpha=0.05. Alpha is the probability of rejecting the null hypothesis of no trend <br /> when it is true(i.e., a Type 1 error). San Joaquin County uses the Sanitas® software to calculate <br /> both the Sen's slope and Mann-Kendall trend. <br /> Progress of Corrective Action Measures A-1 Harney Lane Sanitary Landfill <br /> Revised-August 21,2003 County of San Joaquin <br />