Detection of spatial pattern at several scales simultaneously

1975 ◽  
Vol 7 (03) ◽  
pp. 449-450
Author(s):  
Roger Mead
Keyword(s):  
Spatial Pattern ◽  
Plant Communities ◽  
Random Distribution ◽  
Small Sample ◽  
Pattern Detection ◽  
Ecological Research ◽  
Valid Method ◽  
Distributional Properties ◽  
The Individual ◽  
Plant Ecological

Detection of the different scales of pattern in plant communities is an important area of plant ecological research, and various tests of pattern have been devised. The method of pattern detection which is ecologically most meaningful is that due to Greig-Smith (1952) but, until now, this has suffered from the lack of valid tests of significance for the individual scales of pattern, once the overall departure from a random distribution has been established. Various tests which partially or completely overcome this deficiency are discussed and exemplified and their small sample distributional properties examined. It is concluded that a set of tests, based on randomisation arguments, provides a fully valid method of testing simultaneously for pattern at various scales.

Detection of spatial pattern at several scales simultaneously

1975 ◽  
Vol 7 (3) ◽  
pp. 449-450
Author(s):  
Roger Mead
Keyword(s):  
Spatial Pattern ◽  
Plant Communities ◽  
Random Distribution ◽  
Small Sample ◽  
Pattern Detection ◽  
Ecological Research ◽  
Valid Method ◽  
Distributional Properties ◽  
The Individual ◽  
Plant Ecological

Detection of the different scales of pattern in plant communities is an important area of plant ecological research, and various tests of pattern have been devised. The method of pattern detection which is ecologically most meaningful is that due to Greig-Smith (1952) but, until now, this has suffered from the lack of valid tests of significance for the individual scales of pattern, once the overall departure from a random distribution has been established. Various tests which partially or completely overcome this deficiency are discussed and exemplified and their small sample distributional properties examined. It is concluded that a set of tests, based on randomisation arguments, provides a fully valid method of testing simultaneously for pattern at various scales.

scholarly journals Within-Site Variability of Liana Wood Anatomical Traits: A Case Study in Laussat, French Guiana

Forests ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 523 ◽  
Author(s):  
Félicien Meunier ◽  
Sruthi M. Krishna Moorthy ◽  
Hannes P. T. De Deurwaerder ◽  
Robin Kreus ◽  
Jan Van den Bulcke ◽  
...  
Keyword(s):  
Specific Gravity ◽  
French Guiana ◽  
Growth Form ◽  
Vessel Diameter ◽  
Small Sample ◽  
Diameter Distribution ◽  
Hydraulic Architecture ◽  
Woody Vines ◽  
Wood Trait ◽  
The Individual

Research Highlights: We investigated the variability of vessel diameter distributions within the liana growth form among liana individuals originating from a single site in Laussat, French Guiana. Background and Objectives: Lianas (woody vines) are key components of tropical forests. Lianas are believed to be strong competitors for water, thanks to their presumed efficient vascular systems. However, unlike tropical trees, lianas are overlooked in field data collection. As a result, lianas are often referred to as a homogeneous growth form while little is known about the hydraulic architecture variation among liana individuals. Materials and Methods: We measured several wood hydraulic and structural traits (e.g., basic specific gravity, vessel area, and vessel diameter distribution) of 22 liana individuals in a single sandy site in Laussat, French Guiana. We compared the liana variability of these wood traits and the correlations among them with an existing liana pantropical dataset and two published datasets of trees originating from different, but species-rich, tropical sites. Results: Liana vessel diameter distribution and density were heterogeneous among individuals: there were two orders of magnitude difference between the smallest (4 µm) and the largest (494 µm) vessel diameters, a 50-fold difference existed between extreme vessel densities ranging from 1.8 to 89.3 vessels mm−2, the mean vessel diameter varied between 26 µm and 271 µm, and the individual theoretical stem hydraulic conductivity estimates ranged between 28 and 1041 kg m−1 s−1 MPa−1. Basic specific gravity varied between 0.26 and 0.61. Consequently, liana wood trait variability, even within a small sample, was comparable in magnitude with tree surveys from other tropical sites and the pantropical liana dataset. Conclusions: This study illustrates that even controlling for site and soil type, liana traits are heterogeneous and cannot be considered as a homogeneous growth form. Our results show that the liana hydraulic architecture heterogeneity across and within sites warrants further investigation in order to categorize lianas into functional groups in the same way as trees

scholarly journals The comparison of the scores obtained by Bayesian nonparametric model and classical test theory methods

2021 ◽  
Vol 104 (3) ◽  
pp. 003685042110283
Author(s):  
Meltem Yurtcu ◽  
Hülya Kelecioglu ◽  
Edward L Boone
Keyword(s):  
Classical Test Theory ◽  
Small Sample ◽  
Test Theory ◽  
Nonparametric Model ◽  
Bayesian Nonparametric ◽  
Test Equating ◽  
Classical Test ◽  
A Value ◽  
Item Functioning ◽  
The Individual

Bayesian Nonparametric (BNP) modelling can be used to obtain more detailed information in test equating studies and to increase the accuracy of equating by accounting for covariates. In this study, two covariates are included in the equating under the Bayes nonparametric model, one is continuous, and the other is discrete. Scores equated with this model were obtained for a single group design for a small group in the study. The equated scores obtained with the model were compared with the mean and linear equating methods in the Classical Test Theory. Considering the equated scores obtained from three different methods, it was found that the equated scores obtained with the BNP model produced a distribution closer to the target test. Even the classical methods will give a good result with the smallest error when using a small sample, making equating studies valuable. The inclusion of the covariates in the model in the classical test equating process is based on some assumptions and cannot be achieved especially using small groups. The BNP model will be more beneficial than using frequentist methods, regardless of this limitation. Information about booklets and variables can be obtained from the distributors and equated scores that obtained with the BNP model. In this case, it makes it possible to compare sub-categories. This can be expressed as indicating the presence of differential item functioning (DIF). Therefore, the BNP model can be used actively in test equating studies, and it provides an opportunity to examine the characteristics of the individual participants at the same time. Thus, it allows test equating even in a small sample and offers the opportunity to reach a value closer to the scores in the target test.

scholarly journals MEMGENE: Spatial pattern detection in genetic distance data

2014 ◽  
Vol 5 (10) ◽  
pp. 1116-1120 ◽  
Author(s):  
Paul Galpern ◽  
Pedro R. Peres-Neto ◽  
Jean Polfus ◽  
Micheline Manseau
Keyword(s):  
Genetic Distance ◽  
Spatial Pattern ◽  
Pattern Detection ◽  
Distance Data

scholarly journals Diagnostic Challenges in Newborns and Infants with Coagulation Disorders

2020 ◽  
Vol 40 (01) ◽  
pp. 084-087
Author(s):  
Wolfgang Eberl
Keyword(s):  
Children And Adolescents ◽  
Small Sample ◽  
Laboratory Diagnostics ◽  
Coagulation Disorders ◽  
Small Children ◽  
Preanalytical Phase ◽  
Coagulation Tests ◽  
Strategy Performance ◽  
Performance And Evaluation ◽  
The Individual

AbstractLaboratory diagnostics in children and adolescents, especially in newborns and very small children, differ considerably compared with laboratory diagnostics in adults. This applies to all individual steps of the examination (i.e., the indication, the preanalytical phase, the analysis itself, and interpretation of the findings). This is particularly true in the diagnostics of hemostasis, in which small sample volumes and relatively error prone coagulation tests are posing particular challenges to the strategy, performance, and evaluation of the tests. Differences in the individual steps are illustrated below.

Teacher coaching in New Zealand secondary schools: an exploratory study

2019 ◽  
Vol 8 (2) ◽  
pp. 70-85
Author(s):  
Paul Nathan Bennett
Keyword(s):  
New Zealand ◽  
Secondary Schools ◽  
Small Sample Size ◽  
Small Sample ◽  
Social Construct ◽  
Content Type ◽  
Evaluation Strategies ◽  
Development Approach ◽  
The Individual ◽  
Teacher Coaching

Purpose The purpose of this paper is to explore how teacher coaching is being implemented in New Zealand secondary schools. Design/methodology/approach A pragmatic mixed methods approach was identified as the most suitable. A dominant qualitative approach, using a sequential design, incorporating triangulation of methods and perspectives across time, provided an appropriate research design framework. Findings The findings indicate that teacher coaching is a popular professional development approach that has been enthusiastically implemented throughout New Zealand secondary schools. The four factors of purpose, evaluation, training and funding have been shown to be interrelated factors operating in New Zealand teacher coaching programmes. These factors are perceived to have an influence on teacher coaching programmes achieving their stated objectives. Research limitations/implications A limitation of this study is that it provides a snapshot of teacher coaching in New Zealand secondary schools, and the snapshot presented is constantly changing. A methodological limitation of the study related to the 28 per cent response rate of the questionnaire and the small sample size used for the interview phases. Practical implications This study encourages school leaders to consider if they have defined teacher coaching in the context of their programmes and articulated their objectives. They are persuaded to think about how they could design robust evaluation strategies and targeted training. Social implications The findings show the concept of teacher coaching is a social construct that is influenced not only by unique environmental contexts but also the individual perceptions of all those involved. Originality/value This study provides new knowledge in relation to how and why teacher coaching is being used and the factors that influence whether programme objectives are achieved.

A fistful of shells: amplifying sclerochronological and palaeoclimate signals from molluscan death assemblages

2009 ◽  
Vol 146 (6) ◽  
pp. 917-930 ◽  
Author(s):  
S. HELAMA ◽  
J. K. NIELSEN ◽  
M. MACIAS FAURIA ◽  
I. VALOVIRTA
Keyword(s):  
Sample Size ◽  
Tree Ring ◽  
Small Sample Size ◽  
Low Frequency ◽  
Small Sample ◽  
Pearl Mussel ◽  
Climate Signal ◽  
Growth Variability ◽  
Low Frequency Variability ◽  
The Individual

AbstractA growing body of literature is using sclerochronological information to infer past climates. Sclerochronologies are based on series of skeletal growth records of molluscs that have been correctly aligned in time. Incremental series are obtained from a number of shells to assess the temporal control and improve the climate signal in the final chronology. Much of the sclerochronological theory has been adopted from tree-ring science, due to the longer tradition and more firmly established concepts of chronology construction in dendrochronology. Compared to tree-ring studies, however, sclerochronological datasets are often characterized by relatively small sample size. Here we evaluate how effectively palaeoclimatic signal can be extracted from such a suite of samples. In so doing, the influences of the very basic methods that are applied in nearly every sclerochronological study to remove the non-climatic growth variability prior to palaeoclimatic interpretations, are ranked by their capability to amplify the desired signal. The study is performed in the context of six shells that constitute a bicentennial growth record from annual shell increments of freshwater pearl mussel. It was shown that when the individual series were detrended using the models set by the mean or the median summary curves for ageing (that is, applying Regional Curve Standardization, RCS), instead of fitting the ageing mode statistically to each series, the resulting sclerochronology displayed more low-frequency variability. Consistently, the added low-frequency variability evoked higher proxy–climate correlations. These results show the particular benefit of using the RCS method to develop sclerochronologies and preserve their low-frequency variations. Moreover, calculating the ageing curve and the final chronology by median, instead of mean, resulted in an amplified low-frequency climate signal. The results help to answer a growing need to better understand the behaviour of the sclerochronological data. In addition, we discuss the pitfalls that may potentially disrupt palaeoclimate signal detection in similar sclerochronological studies. Pitfalls may arise from shell taphonomy, water chemistry, time-variant characters of biological growth trends and small sample size.

Sign in / Sign up

Export Citation Format

Share Document