10 RELATIONSHIP BETWEEN LOG s AND LOG w AT NS-201 _ \ log s = 0.20 - 0.46 log w OR Oo STANDARD DEVIATION (s) in nCilg [ «1.58 w 0-46 L n=5 CORRELATION IN LOG SCALE = 0.96 0.1 i. 4 pod 1 bl 10 1 20 i pf 50 100 ALIQUOT SIZE (w) IN GRAMS Figure 2. Estimated Relationship Between Log s and Log w for the Composite Soil Sample Collected Approximately 150 ft North of GZ at NS-201. Suppose we want to estimate the mean Am concentration of a field sample by withdrawing n independent aliquots of a given size w. The variance Va of the resulting x is s?/n. Hence, using Equation (3) we obtain V,= 2.5/nw* 92, A (5) Now, consider the cost of counting an aliquot of soil for Am on a Ge(Li) system. Let us assume that a counting laboratory will charge the same rate, of, say, K dollars per aliquot, for any aliquot size that can be counted without special counting procedures. Thus, we assume that the total Am Ge(Li) analysis cost (C) for n aliquots from a field sample does not depend on w. That is, C = nK or n=C/K. (6) 415