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11 <br />11 <br />F, <br />Appendix 1 5 <br />randomly selected. The number of samples to be collected <br />was set at thirty based on several factors. First, the <br />number of samples to be taken were calculated using the <br />Klee and Carruth formula (See attachment A) . This <br />indicated that the optimum number of samples were 40 at <br />the 1% level of precision and 12 at the 2% level of <br />precision. The Central Limit Theorem indicates that <br />large sample sizes (thirty or greater) tend to be <br />normally distributed around the mean. Based on this, and <br />information supplied by the Integrated Waste Management <br />Board at its workshop in Palo Alto, California, on April <br />20, 1990, the County decided to select thirty as the <br />number of samples to be taken. <br />From each load, a random sample of approximately one <br />cubic yard was collected. The waste was then sorted by <br />waste category and type and placed into plastic <br />containers. Using a hanging scale with a capacity of 250 <br />pounds and an accuracy to one-tenth of a pound, each <br />waste type was weighed and recorded. This data was later <br />input into a computer program which tabulated the weights <br />and calculated percentages and statistical information. <br />The methodologies used, including the number of <br />samples taken and the analysis performed, were discussed <br />with Integrated Waste Management Board staff. Staff <br />indicated that the methodology was beyond that required <br />by the guidelines. <br />During the sampling, commercial and industrial drop <br />boxes often contained only a few types of material, for <br />example heavy sheet plastic, wood pallets, and corrugated <br />paper. These bulky loads did not lend themselves to the <br />intensive sort and weigh methods used on residential and <br />small business wastes. In these cases, relative <br />percentages by weight for the component materials were <br />estimated for the entire load, and those percentages were <br />applied to an average sample weight of 250 lbs.. <br />11 <br />F, <br />Appendix 1 5 <br />