125,032 research outputs found
The analysis of very small samples of repeated measurements I: an adjusted sandwich estimator
No full textThe statistical analysis of repeated measures or longitudinal data always requires the accommodation of the
covariance structure of the repeated measurements at some stage in the analysis. The general linear mixed
model is often used for such analyses, and allows for the specification of both a mean model and a covariance
structure. Often the covariance structure itself is not of direct interest, but only a means to producing valid inferences about the response. Existing methods of analysis are often inadequate where the sample size is small. More precisely, statistical measures of goodness of fit are not necessarily the right measure of the appropriateness of a covariance structure and inferences based on conventional Wald type procedures do not approximate sufficiently well
their nominal properties when data are unbalanced or incomplete. This is shown to be the case when adopting
the Kenward-Roger adjustment where the sample size is very small. A generalization of an approach to Wald tests using a bias adjusted empirical sandwich estimator for the covariance matrix of the fixed effects from generalized estimating equations is developed for Gaussian repeated measurements. This is shown to attain the correct test size but has very low power
The analysis of very small samples of repeated measurements II: a modified box correction
No full textThere is a need for appropriate methods for the analysis of very small samples of continuous repeated measurements. A key feature of such analyses is the role played by the covariance matrix of the repeated observations. When subjects are few it can be difficult to assess the fit of parsimonious structures for this matrix, while the use of an unstructured form may lead to a serious lack of power. The Kenward-Roger adjustment is now widely adopted as a means of providing an appropriate inferences in small samples, but does not perform adequately in very small samples. Adjusted tests based on the empirical sandwich estimator can be constructed that have good nominal properties, but are seriously underpowered. Further, when such data are incomplete, or unbalanced, or non-saturated mean models are used, exact distributional results do not exist that justify analyses with any sample size. In this paper, a modification of Box's correction applied to a linear model based -statistic is developed for such small sample settings and is shown to have both the required nominal properties and acceptable power across a range of settings for repeated measurements
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Supplementary materials to "Large-scale disruptive activism strengthened environmental attitudes in the United Kingdom"
No full textSupplementary materials to: Kenward, B., & Brick, C. (2024). Large-scale disruptive activism strengthened environmental attitudes in the United Kingdom. Global Environmental Psychology, 2, Article e11079. https://doi.org/10.5964/gep.11079The supplementary material includes supplementary acknowledgements, figures/tables, detailed procedure explanations, data history statement.unknownunknow
The Analysis of Very Small Samples of Repeated Measurements
No full textThe statistical analysis of repeated measures or longitudinal data always requires the
accommodation of the covariance structure of the repeated measurements at some
stage in the analysis. The general linear mixed model is often used for such analyses,
and allows for the specification of both a mean model and a covariance structure.
Often the covariance structure itself is not of direct interest, but only a means to
producing valid inferences about the response. This thesis considers methods for
the analysis of repeated measurements which arise from very small samples.
In Part 1, existing methods of analysis are shown to be inadequate for very small
samples. More precisely, statistical measures of goodness of fit are not necessarily
the right measure of the appropriateness of a covariance structure and inferences
based on conventional Wald type procedures (with small sample adjustments) do
not approximate sufficiently well their nominal properties when data are unbalanced
or incomplete.
In Part 2, adaptive-estimation techniques are considered for the sample covariance
matrix which smooth between unstructured and structured forms; 'direct' smoothing, a weighted average of the unstructured and structured estimates, and an estimate chosen via penalised likelihood. Whilst attractive in principle, these approaches are shown to have little success in practice, being critically dependent on
the 'correct' choice of smoothing structure.
Part 3 considers methods which are less dependent on the covariance structure. A
generalisation of a small sample adjustment to the empirical sandwich estimator
is developed which accounts for its inherent bias and increased variance. This has
nominal properties but lacks power. Also, a modification to Box's correction, an
ANOVA F-statistic which accounts for departures from independence, is given which
has both nominal properties and acceptable power.
Finally, Part 4 recommends the adoption of the modified Box statistic for repeated
measurements data where the sample size is very small
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Biodiversity and ecosystem services in the Frome catchment, Purbeck district, United Kingdom
No full textA map for valuing ecosystem services in the 480 km2 Frome catchment, to investigate scenarios of change in land use, was internet crowd-sourced. Scouts mapped deer habitats in 15% of the 30 km2 Arne Parish, while 143 residents volunteered data on deer sightings in the 5-year community survey
Pragmatic Case Studies as a Source of Unity in Applied Psychology
No full textTo unify or not to unify applied psychology: that is the question. In this article we review pendulum swings in the historical efforts to answer this question—from a comprehensive, positivist, “top-down,” deductive yes between the 1930s and the early 60s, to a postmodern no since then. A rationale and proposal for a limited, “bottom-up,” inductive yes in applied psychology is then presented, employing a case-based paradigm that integrates both positivist and postmodern themes and components. This paradigm is labeled “pragmatic psychology” and, its specific use of case studies, the “Pragmatic Case Study Method” (“PCS Method”). We call for the creation of peer-reviewed journal-databases of pragmatic case studies as a foundational source of unifying applied knowledge in our discipline. As one example, the potential of the PCS Method for unifying different angles of theoretical regard is illustrated in an area of applied psychology, psychotherapy, via the case of Mrs. B. The article then turns to the broader historical and epistemological arguments for the unifying nature of the PCS Method in both applied and basic psychology.Peer reviewe
Clinical diagnosis of Achilles tendinopathy with tendinosis.
No full textOBJECTIVE: To evaluate sensitivity, specificity, reproducibility, and predictive value of palpation of the painful arc sign and of the Royal London Hospital test in 10 patients with Achilles tendinopathy and in 14 asymptomatic subjects. DESIGN: Test-retest study. SETTING: University teaching hospital. PARTICIPANTS: Ten male athletes on the waiting list for exploration of one of their Achilles tendons for tendinopathy of the main body of the tendon attended a special clinic. Each was invited to bring at least one athlete of the same sex in the same discipline aged within 2 years of themselves with no history and no symptoms of Achilles tendinopathy. A total of 14 controls were thus recruited. MAIN OUTCOME MEASURES: Pain and tenderness following performance of palpation, the painful arc sign, and the Royal London Hospital test. RESULTS: There were no statistically significant differences at the 5% level among the effects of investigator or between morning and afternoon measurements for any of the three measurement methods. There was no evidence of a difference of the three assessment methods (p > 0.05). When the three methods were combined, the overall sensitivity was 0.586 (confidence interval [CI], 0.469-0.741), and the overall specificity was 0.833 (CI, 0.758-0.889). CONCLUSIONS: In patients with tendinopathy of the Achilles tendon with a tender area of intratendinous swelling that moves with the tendon and whose tenderness significantly decreases or disappears when the tendon is put under tension, a clinical diagnosis of tendinopathy can be formulated, with a high positive predictive chance that the tendon will show ultrasonographic and histologic features of tendinopathy
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