Distribution 02
Distribution 02 : (a) This is a general term for the dispersal of a xenobiotic and its derivatives throughout an organism or environmental system. [Duffus, 2000: Univ. Edinburgh Med School On-line Chemical Safety Glossary]; (b) The complete summary of the frequencies of the values or categories of a measurement made on a group of persons. The distribution tells either how many or what proportion of the group were found to have each value (or each range of values) out of all the possible values that the quantitative measure can have. [Last, 1983: A Dictionary of Epidemiology]; (c) The pattern by which parasite numbers are partitioned amongst available hosts. If the fraction of the population who have i parasites is p(i) then the distribution is the set of numbers p(0),p(1), p(2), ... . Summary statistics of this distribution include prevalence (1_p(0)) and mean intensity ( p(1)+ 2p(2)+ 3p(3)+.. Useful distributions include the Poisson and negative binomial. [Swinton, 1999: A Dictionary of Epidemiology]; (d) A set of values derived from a specific population or set of measurements that represents the range and array of data for the factor being studied. [USEPA, 1997b: Exposure Factors Handbook]
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