Permutation Tests

Good, Phillip I.

doi:10.1007/978-1-4757-3235-1

Cited by 545 publications

(75 citation statements)

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“…This additional test consisted of repeating 1000 times the same classification procedure but using random labels. In this way we were able to estimate the probability that an accuracy rate was obtained by chance (Good, 2000). A p -value was then computed as the number of repeats where the accuracy obtained with the random labels was larger than that obtained with the true labels, divided by 1000.…”

Section: Methodsmentioning

confidence: 99%

Identifying endophenotypes of autism: a multivariate approach

Segovia

Holt

Spencer

et al. 2014

Front. Comput. Neurosci.

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The existence of an endophenotype of autism spectrum condition (ASC) has been recently suggested by several commentators. It can be estimated by finding differences between controls and people with ASC that are also present when comparing controls and the unaffected siblings of ASC individuals. In this work, we used a multivariate methodology applied on magnetic resonance images to look for such differences. The proposed procedure consists of combining a searchlight approach and a support vector machine classifier to identify the differences between three groups of participants in pairwise comparisons: controls, people with ASC and their unaffected siblings. Then we compared those differences selecting spatially collocated as candidate endophenotypes of ASC.

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Section: Methodsmentioning

confidence: 99%

Identifying endophenotypes of autism: a multivariate approach

Segovia

Holt

Spencer

et al. 2014

Front. Comput. Neurosci.

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“…The data collected in the present report represent repeated measurements (for lumen diameter eight measurements points, for blood¯ow velocity six measurement points, see Figs 1 and 2). For the comparison of repeated measurements a summary statistic as area under the curve (AUC) is often recommended (Crowder, 1990;Good, 2000). Therefore, in the present analysis all measurement points from 0 to 170 s (n 8 for lumen diameter), and from 0 to 180 s (n 6 for blood¯ow velocity) were used to calculate the AUC for each subject and each experiment.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, in the present analysis all measurement points from 0 to 170 s (n 8 for lumen diameter), and from 0 to 180 s (n 6 for blood¯ow velocity) were used to calculate the AUC for each subject and each experiment. By use of a nonparametric test for paired comparisons, not based on ranks but original values (Good, 2000), the P-values were calculated exactly. Lumen diameter 120 s after cuff de¯ation was prespeci®ed for analysis according to results in a previous paper (Wendelhag et al, 1999), and therefore a P-value was calculated also for this measurement point.…”

Section: Methodsmentioning

confidence: 99%

Post-occlusion brachial artery vasodilatation after ischaemic handgrip exercise is nitric oxide mediated

Agewall¹,

Hulthe²,

Fagerberg³

et al. 2002

Clin Physiol

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Flow-mediated vasodilatation (FMD) of the brachial artery is used as a measure to quantify endothelial dysfunction. However, FMD after occlusion only is small in healthy people over middle age, but can be increased after handgrip exercise. The aim of this study was to evaluate whether postocclusion vasodilatation after handgrip exercise is mediated by nitric oxide (NO). High frequency ultrasound was used to measure brachial artery diameter at rest and after reactive hyperaemia with and without handgrip exercise during NaCl or NG-monomethyl-L-arginine (L-NMMA) infusion in healthy 60-year-old men. Postocclusion vasodilation was significantly larger after handgrip exercise compared with occlusion only (P=0.0078). Postocclusion vasodilatation was significantly lower after ischaemic handgrip exercise during intra-arterial infusion of L-NMMA compared with infusion of NaCl (P = 0.039). It may be concluded that the increased postocclusion brachial artery vasodilatation observed after ischaemic handgrip exercise is at least partly NO mediated. This modification of the investigation procedure may improve our ability to quantify FMD in subjects with and without vascular disease.

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“…In synthesizing randomized clinical trials, their idea is based on the rerandomization argument considering that the active treatment and control groups within a trial form a "pair." Further, their idea can be more generally interpreted as an adaptation of the one-sample permutation test based on the symmetric assumptions of test statistics around the null value (Good, 2000). First, we developed an extended exact permutation method for joint inference of the grand mean vector μ of the multivariate random-effects model (*).…”

Section: Methodsmentioning

confidence: 99%

Permutation inference methods for multivariate meta‐analysis

2019

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Multivariate meta‐analysis is gaining prominence in evidence synthesis research because it enables simultaneous synthesis of multiple correlated outcome data, and random‐effects models have generally been used for addressing between‐studies heterogeneities. However, coverage probabilities of confidence regions or intervals for standard inference methods for random‐effects models (eg, restricted maximum likelihood estimation) cannot retain their nominal confidence levels in general, especially when the number of synthesized studies is small because their validities depend on large sample approximations. In this article, we provide permutation‐based inference methods that enable exact joint inferences for average outcome measures without large sample approximations. We also provide accurate marginal inference methods under general settings of multivariate meta‐analyses. We propose effective approaches for permutation inferences using optimal weighting based on the efficient score statistic. The effectiveness of the proposed methods is illustrated via applications to bivariate meta‐analyses of diagnostic accuracy studies for airway eosinophilia in asthma and a network meta‐analysis for antihypertensive drugs on incident diabetes, as well as through simulation experiments. In numerical evaluations performed via simulations, our methods generally provided accurate confidence regions or intervals under a broad range of settings, whereas the current standard inference methods exhibited serious undercoverage properties.

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Permutation Tests

Cited by 545 publications

References 0 publications

Identifying endophenotypes of autism: a multivariate approach

Identifying endophenotypes of autism: a multivariate approach

Post-occlusion brachial artery vasodilatation after ischaemic handgrip exercise is nitric oxide mediated

Permutation inference methods for multivariate meta‐analysis

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