cattle would be expected to comprise a composite random sample of the vegetation and soils present in the compound, and the contribution of each sampling stratum to the herd's composite diet of vegetation and soil would be proportional to the area of the sampling stratum divided by the total area of the compound. In subsequent sections of this report, the means and standard deviations of I., C,I1_, and C_ will be estimated. These estimates of population parameters, wp and o, and a random number generator described in Appendix I will be used to generate synthetic composite random samples of I which are iterative solutions of Equation 1 for which each of the’ four factors on the right side of the equation is an independent random variable specified by its estimated mean and standard deviation. The means and standard deviations of these synthetic samples will provide the basis for generating synthetic composite random samples of I Comparing these simulation results with the previous estimates of4t ; described in the Introduction, should provide a rough idea of the probable accuracy of Tou estimation in general. Vegetation Ingestion Rate The fistulated steer data mentioned in the introduction and discussed elsewhere in this volume (see the article by D. D. Smith) provide the best empirical basis for estimating rates of vegetation ingestion by cattle grazing the inner compound of Area 13. At this writing, however, the only data at hand are the concentrations (nCi/kg) of plutonium in the vegetation and fluid components of rumen contents. Data concerning the weights of these components, the body weights of the fistulated steers, and the fraction of daily intake represented by a 24-hour rumen sample are also required for estimating I While simulation studies based on fistulated steer data will be defurred until the complete data set is available for examination, it is worth noting here that the plutonium concentrations published in Appendices III and IV of Smith's paper (this volume) appear to be lognormally distributed and that this is quite in line with expectations based on examination of other data sets concerning the distribution of plutonium in Area 13. For simulation purposes, estimates of vegetation ingestion rates are based on a theoretical model formulated as follows: I, = 163.5 wo-73/4.5 D (2) where I is the vegetation ingestion rate, g/day, 1863.5 W9-73 is the digestible energy, kcal/day, required for main~ tenance of an adult cow (Siegmund, ed., 1967), Wis the total live body weight, kg, of the cow, 4.5 keal/g is the caloric value of most plant materials (Golley, and 1961), Dis the digestibility (dimensionless) of ingested vegetation. 486