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Mark and recapture is a method commonly used in ecology to estimate an animal population's size. A portion of the population is captured, marked, and released. Later, another portion is captured and the number of marked individuals within the sample is counted. Since the number of marked individuals within the second sample should be proportional to the number of marked individuals in the whole population, an estimate of the total population size can be obtained by dividing the number of marked individuals by the proportion of marked individuals in the second sample. The method is most useful when it is not practical to count all the individuals in the population. Other names for this method, or closely related methods, include capture-recapture, capture-mark-recapture, mark-recapture, sight-resight, mark-release-recapture, multiple systems estimation, band recovery, the Petersen method, and the Lincoln method. Another major application for these methods is in epidemiology,〔Chao, A., Tsay, P. K., Lin, S. H., Shau, W. Y., and Chao, D. Y., 2001, The applications of capture-recapture models to epidemiological data, Statistics in Medicine, volume 20, issue 20, pages 3123–3157, doi 10.1002/sim.996〕 where they are used to estimate the completeness of ascertainment of disease registers. Typical applications include estimating the number of people needing particular services (i.e. services for children with learning disabilities, services for medically frail elderly living in the community), or with particular conditions(i.e. illegal drug addicts, people infected with HIV, etc.). == Field work related to mark-recapture == Typically a researcher visits a study area and uses traps to capture a group of individuals alive. Each of these individuals is marked with a unique identifier (e.g., a numbered tag or band), and then is released unharmed back into the environment. A mark recapture method was first used for ecological study in 1896 by C.G. Johannes Petersen to estimate plaice, ''Pleuronectes platessa'', populations.〔Southwood, T.R.E. & Henderson, P. (2000) ''Ecological Methods'', 3rd edn. Blackwell Science, Oxford.〕 Sufficient time is allowed to pass for the marked individuals to redistribute themselves among the unmarked population. Next, the researcher returns and captures another sample of individuals. Some individuals in this second sample will have been marked during the initial visit and are now known as recaptures. Other animals captured during the second visit will not have been captured during the first visit to the study area. These unmarked animals are usually given a tag or band during the second visit and then are released. Population size can be estimated from as few as two visits to the study area. Commonly, more than two visits are made, particularly if estimates of survival or movement are desired. Regardless of the total number of visits, the researcher simply records the date of each capture of each individual. The "capture histories" generated are analyzed mathematically to estimate population size, survival, or movement. In the epidemiological setting, different sources of patients take the place of the repeated field visits in ecology. To take a concrete example, establishing a register of children with Type 1 diabetes children were identified from hospital admission records, from general practitioners (family doctors), and from the records of the local Diabetes Association. None of these sources had a complete list, but by putting them together it was possible to do two things, first to see how many children were identified in total, and secondly to estimate how many more children with Type 1 diabetes were living in the vital community. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mark and recapture」の詳細全文を読む スポンサード リンク
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