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Sample (material)

About: Sample (material) is a research topic. Over the lifetime, 2893 publications have been published within this topic receiving 28646 citations. The topic is also known as: samples & single sample.


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Journal ArticleDOI
TL;DR: Information content may be used as a measure of the diversity of a many-species biological collection whereby the sample size is progressively increased by addition of new quadrats and the mean increment in total diversity that results from enlarging the sample still more provides an estimate of the Diversity per individual in the whole population.

4,415 citations

Journal ArticleDOI
01 Jul 1948-Ecology
TL;DR: The purpose of this paper is to deduce, from a number of examples and from theoretical considerations, some plausible general law as to how abundance or commonness is distributed among species.
Abstract: The purpose of this paper is to deduce, from a number of examples and from theoretical considerations, some plausible general law as to how abundance or commonness is distributed among species. Experimentally, this could be done by making a complete census of every species, but, with rare exceptions, this procedure is quite impractical. We therefore attempt to deduce the "universe" from a sample. Commonness, as understood by ecologists, has several rather different meanings: we are here concerned with (1) the total number of living individuals of a given species, which might be called its global abundance, (2) the total number of individuals living at any instant on a given area, such as on an acre or a square mile, which might be called its local abundance, (3) the ratio which the number of individuals or one species bears to that of another species, i.e., its relative abundance, and (4) the number of individuals observed, for example, the number of a moth species counted in a sample from a light trap, its "observed," "apparent," or "sample" abundance. There will not usually be any difficulty in deciding which phase of the subject is under discussion at any time. The Raunkiaer "Index of Frequency" is a measure of ubiquity rather than of commonness as above defined: its relation to our other concepts is discussed later. As a rule, we are interested in a sample only in so far as it throws light upon the "universe" that is being sampled. The sample will be a sufficiently accurate replica of the universe provided (1) it is a perfectly "random" sample, and (2) no species is represented in the sample by less than 20 or 30 individuals. In most ecological work condition (2) will never obtain, and much of the present paper will center on this difficulty. Condition (1) will not usually obtain in the broadest sense, and needs a moment's consideration. A geologist sampling an ore-body, whose boundaries have been delimited accurately by previous exploration, has a known "universe" and merely needs information on composition. His universe is permanent. But in ecological work, the "universe" changes rapidly. The moths flying tonight are not those that flew a month ago, or will fly a month hence. Those flying this year are a vastly different association from those that flew last year in the same area. The same thing is true of rodent populations, of birds, and of plants. We are dealing with a fleeting and fluctuating assemblage, a "universe" continually expanding, contracting, and changing in composition. Thus it is important to recognize at the outset that, for the purposes of our present investigation, the "universe" from which the sample is drawn is that universe declared to us by the sample itself, and not our preconceived notion of what the universe ought to be. Further, it is important to recognize that the randomness we seek is merely randomness with respect to commonness or rarity. A light trap is satisfactory in this respect and samples its own universe appropriately. It is definitely selective in respect of phototropism, but it is random in respect of commonness, i.e., it does not care which of two moths, equally phototropic, it catches, though one may be a great rarity and the other of a very common species. On the other hand, an entomologist, or even an intelligent boy, with a net, is not a satisfactory collector, for he will go after the rarity. For this reason we have to reject Corbet's ('41)

1,787 citations

Journal ArticleDOI
TL;DR: In this article, it is argued that the more indubitably it is known that the upper group is superior to the lower group, the more definitely can it be concluded that an item is valid by finding that the item is more successful in passing it than the lower groups.
Abstract: It is not intended here to discuss the general problem of item validation, but only that aspect of it thai arises when an upper and lower group are selected to serve as standard groups in the differentiation of test items. It is argued that the more indubitably it is known that the upper group is superior to the lower group, the more definitely can it be concluded that an item is valid by finding that the upper group is more successful in passing it than the lower group. If, in two situations, one in which the upper and lower groups are differentiated with high certainty and the other with little certainty, the proportion of passes (i.e., right answers) in the upper groups are equal and equally superior to the proportion of passes in the lower groups, we should believe that the item represented in the first situation is more valid than that of the second situation. Having available an initial group which is normally distributed with reference to a desired criterion, we set the problem of selecting upper and lower portions of this group which will be most efficient in the study of items, and their selection or rejection. The items in question are capable of two grades only, right or wrong. We further limit the issue by not here considering the interrelationship of items, a matter of first importance when the final test to be constructed is to contain more than one item. It is granted that the problem as set is too constricted to be "real," but it is, nevertheless, believed that its solution is commonly pertinent to the handling of real item selection problems. The writer has stated that twenty-seven per cent should be selected at each extreme to yield upper and lower groups which are most indubitably different with respect to the trait in question. This article does not alter that conclusion but does provide a more available and somewhat improved derivation. Let us be given graduated scores on a test or trait from a sample of size N. For simplicity we shall consider N to be even, so that we may

539 citations

Journal ArticleDOI
TL;DR: In this article, a log-linear model for capture-recapture experiments is presented, and its advantages and disadvantages are discussed, and the use of residual patterns and analysis of subsets of data to identify behavioral patterns and acceptable models is emphasised and illustrated with two examples.
Abstract: SUMMARY Log-linear models are developed for capture-recapture experiments, and their advantages and disadvantages discussed. Ways in which they can be extended, sometimes with only partial success, to open populations, subpopulations, trap dependence, and long chains of recapture periods are presented. The use of residual patterns, and analysis of subsets of data, to identify behavioural patterns and acceptable models is emphasised and illustrated with two examples. 1. Capture-Recapture The biological problem with which we are concerned is that of estimating the parameters of a free-living population of unknown size, from a sequence of s samples, in each of which any individual either is or is not observed. The models in this paper require that each animal be marked, naturally or artificially, in such a way that we can observe the numbers of animals which have any particular pattern of being or not being observed through the sequence of samples. There are t = (2s - 1) different observable patterns, which we shall refer to as capture histories, although there is no requirement for physical capture, and denote each pattern by a sequence of l's and 2's representing, respectively, seen or not seen in a particular sample. A general pattern of capture history will be denoted a, with ra, the number of individuals observed to have this pattern. Thus, for example, with s = 3 samples and a = 121, r,2, is the number of animals seen in the first and third samples but not in the second. The pattern with all 2's is by definition unobservable. In general, the population will be subject to demographic change by birth or immigration and by death or emigration. The simplest assumption for the response of an animal to the observer, one which underlies the classical Petersen, Schnabel, or Jolly-Seber estimators, is that every animal alive in the population at a sampling time has the same probability of being observed. This probability may vary from one sample to another or be constant over all, or a number of, samples. If this assumption fails it may do so for either or both of two reasons. The first is that of trap dependence, the probability of an individual being observed in a sample depending on its past history of capture. The second is that of heterogeneity between individuals who, because of differences in their behaviour or in where they live, inherently have different probabilities of being observed in any sample. The basic idea of heterogeneity refers to properties of individuals which remain constant over time, but individual animals may also have time-varying behaviour, the aspect most commonly considered being temporary departure of an individual from the population. Various excellent texts describe theoretical and practical aspects of capture-recapture, notably the comprehensive one by Seber (1982), the introduction by Begon (1979), the

316 citations

Patent
08 Feb 1991
TL;DR: In this article, an analytical apparatus of components of a sample liquid which monitors the state of the sample liquid to be introduced into a piping and prevents mixing-in of a component which lowers the precision of the component analysis is obtained.
Abstract: PURPOSE:To obtain an analyzing apparatus of components of a sample liquid which monitors the state of the sample liquid to be introduced into a piping and prevents mixing-in of a component which lowers the precision of a component analysis. CONSTITUTION:In a stage before a sample liquid is supplied to an automatic flow passage selector valve 1, the water quality of the sample liquid is monitored by providing a water quality monitoring sensor 40. On the basis of an output of this water quality monitoring sensor 40, it is monitored whether or not a component being inadequate on the occasion of analysis of a metal component mixes in the sample liquid, and when the sample liquid is unsuitable for the analysis of the metal component, it is excluded to an external system.

300 citations


Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20252
20241
20237,673
202216,906
2021213
2020125