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aOLE 9-1. (Continued) <br /> Terminology Symbol Mathematical equation (Equation) <br /> Standard deviation of s s = s2 (4) <br /> sample <br /> • Standard error sX sX s (5} <br /> (also standard error <br /> Of mean and standard <br /> deviation of mean) <br /> of sample <br /> • Confidence interval CI CI = A + t.20 SX, with t.20- (6) <br /> for pa obtained from <br /> Table 2 for <br /> appropriate <br /> degrees of freedom <br /> • Regulatory thresholda RT Defined by EPA (e.g., 100 ppm for (7) <br /> barium in elutriate of EP toxicity) <br /> t2 s2 <br /> Appropriate number of n n '22 , with b = RT - z (8) <br /> samples to collect from d <br /> a solid waste (financial <br /> f constraints not considered) <br /> • Degrees of freedom df df n - 1 <br /> (g) <br /> • Square root transformation --- Xi + 1/2 (10) <br /> • Aresin transformation --- Aresin p; if necessary, refer to any (11) <br /> text on basic statistics; <br /> measurements must be con- <br /> verted to percentages (p) <br /> aThe upper limit of the CI for p is compared with the applicable regulatory <br /> threshold (RT) to determine if a solid waste contains the variable (chemical <br /> contaminant) of concern at a hazardous level. The contaminant of concern is not <br /> considered to be present in the waste at a hazardous level if the upper limit of the CI <br /> is less than the applicable RT. Otherwise, the opposite conclusion is reached. <br /> NINE - 3 <br /> Revision O <br /> Date Sept—ecEir 1986 <br />