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Randomization Procedure (randomization + procedure)
Selected AbstractsHigh within-individual variation in total mercury concentration in seabird feathersENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2008Alexander L. Bond Abstract To our knowledge, no rigorous assessment of the variation in mercury concentrations within individual seabirds has been made using multiple body feathers. We analyzed five feathers from individual Arctic terns (Sterna paradisaea Pontoppidan), common terns (Sterna hirundo L.), and Leach's storm-petrels (Oceanodroma leucorhoa Veillot) and found levels of within-individual variability higher than population or time-series variation. Using a randomization procedure, we found a large range of possible mercury concentrations if only one feather per individual had been sampled. Researchers should report within-individual variability in future studies. [source] The proportion heuristic: problem set size as a basis for performance judgmentsJOURNAL OF BEHAVIORAL DECISION MAKING, Issue 3 2001David H. Silvera Abstract How do people evaluate their degree of mastery over a task? A series of four studies demonstrated that a potentially irrelevant cue can have a strong influence on such evaluations. In these studies, the total amount of work given to participants (the problem set size) influenced both (a) the amount of work participants completed before feeling that they had performed well and were adequately prepared for a related future task, and (b) participants' assessments of their performance and their feelings of preparedness for a related future task. These effects occurred even when a randomization procedure was used to emphasize the arbitrary nature of the problem set size. The effects vanished, however, when participants were given extra time to evaluate their progress after completing each problem. Copyright © 2001 John Wiley & Sons, Ltd. [source] clonality V.0.4: a randomization-based program to test for heterozygosity-genet size relationships in clonal organismsMOLECULAR ECOLOGY RESOURCES, Issue 5 2008FRANCK PRUGNOLLE Abstract clonality V.0.4 is a program for testing heterozygosity-genet size relationships in clonal organisms using a randomization procedure. The software has been developed under the Borland Delphi developing environment and a Windows-executable version is freely downloadable from http://gemi.mpl.ird.fr/SiteSGASS/Prugnolle/ClonalityPage.html. The program compares the observed FIS of the population with the FIS expected if genets (multilocus genotypes present in multiple copies within the population) were chosen randomly from the set of different multilocus genotypes. The randomization procedure is performed with the same number of genets and the same number of repetitions per genet as what is observed in the original data set. [source] The relative importance of spatial aggregation and resource partitioning on the coexistence of mycophagous insectsOIKOS, Issue 1 2005Kazuo H. Takahashi The relative importance of spatial aggregation and resource partitioning on coexistence was investigated for mycophagous insects in central Japan. The effects of spatial aggregation and resource partitioning were separated by a randomization procedure. From 124 patches of macrosporophores belonging to 37 species, 3275 individuals belonging to 14 families of Diptera and 11 individuals to Lepidoptera emerged. Since the level of identification varied among insect taxa, the analysis was made in three ways; 1) for all taxa to assess the stability of the whole community, 2) for drosophilid species to assess their persistence in the community, and 3) for species of Drosophila and Mycodrosophila to assess their persistence against congeneric and heterogeneric species. Both spatial aggregation and resource partitioning functioned for the stability of whole mycophagous insect community, and spatial aggregation played a more important role than resource partitioning. On the other hand, only spatial aggregation functioned for the persistence of drosophilid species in the community. According to the analysis on species of Drosophila and Mycodrosophila against congeneric and heterogeneric species, the relative importance of resource partitioning was smaller for the coexistence of within-genus species pairs than for that of between-genus species pairs. These results suggest that the relative importance of these two mechanisms depends on the phylogenetic and guild diversity of community. [source] How good is the fossil record of arthropods?GEOLOGICAL JOURNAL, Issue 3-4 2001An assessment using the stratigraphic congruence of cladograms Abstract A total of 179 published cladograms of arthropods was tested for their congruence with the palaeontological record. Congruence for data sets including 510 tetrapod and 157 fish trees was also calculated for comparison. Results provide support for the hypothesis that the fossil record of arthropods is less complete (at levels of stratigraphic and taxonomic resolution pertinent to most macroevolutionary studies) than the records of several other taxa. Differences in tree size, shape, balance and the distribution of first stratigraphic appearances (potential sources of bias) were controlled for by various randomization procedures. Most measures of congruence for arthropods were statistically poorer than those for other groups, even when the sample was divided into broad temporal bins. Many of the most robust and widely reproduced sister groupings of arthropods are attended by ghost ranges of many tens or hundreds of millions of years. Fossils of a number of presently very diverse and abundant arthropod groups are conspicuously absent from the record, despite many spectacular examples of the detailed preservation of others. There is probably no single reason for the apparently poor record of arthropods. Low preservation potential, small size of individuals, small numbers of individuals, and restricted palaeobiogeography almost certainly play a role in particular cases. Copyright © 2001 John Wiley & Sons, Ltd. [source] Randomization in psychiatric intervention research in the general practice settingINTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 3 2000CM Van Der Feltz-Cornelis Faculty of Medicine Abstract Most studies of psychiatric interventions in general practice settings conform only in part to the requirements of randomization, placebo control and blinding as formulated by the Cochrane Collaboration. It is possible, nonetheless, to develop experimental research designs that are sufficiently near to this standard. These must deal with certain methodological issues specific to psychiatric research. This article discusses scientific standards of psychiatric research with special consideration of interventions in general practice settings. These issues are accompanied by concrete examples and suggestions on how to confront the problems. In psychiatric intervention research, equivalence studies with single-blind outcome assessment, a tested and ethically justified method, are generally used in place of placebo-controlled studies. The article also examines randomization procedures in greater depth. Randomization can be applied across trial subjects or across doctors' practices. Practical consequences of randomizing across subjects, and specific implementations of it such as crossover and pre-post designs in general practice settings, are clarified. Overall, a research design using randomization across doctors' practices is judged preferable to one that randomizes across trial subjects. One potential problem is that the control group may become too small, especially when considerable effects are expected from the intervention being studied. One might consider making the control condition smaller in the first place, or, if indicated on ethical grounds, performing an intermediate analysis and then breaking off the study as soon as a statistically significant effect has been demonstrated. Multilevel statistical techniques offer new opportunities for analysis within such designs. Copyright © 2000 Whurr Publishers Ltd. [source] | ||||||||||