journal
MENU ▼
Read by QxMD icon Read
search

Biometrics

journal
https://www.readbyqxmd.com/read/28099998/a-generalized-levene-s-scale-test-for-variance-heterogeneity-in-the-presence-of-sample-correlation-and-group-uncertainty
#1
David Soave, Lei Sun
We generalize Levene's test for variance (scale) heterogeneity between k groups for more complex data, when there are sample correlation and group membership uncertainty. Following a two-stage regression framework, we show that least absolute deviation regression must be used in the stage 1 analysis to ensure a correct asymptotic χk-12/(k-1) distribution of the generalized scale (gS) test statistic. We then show that the proposed gS test is independent of the generalized location test, under the joint null hypothesis of no mean and no variance heterogeneity...
January 18, 2017: Biometrics
https://www.readbyqxmd.com/read/28099997/on-joint-estimation-of-gaussian-graphical-models-for-spatial-and-temporal-data
#2
Zhixiang Lin, Tao Wang, Can Yang, Hongyu Zhao
In this article, we first propose a Bayesian neighborhood selection method to estimate Gaussian Graphical Models (GGMs). We show the graph selection consistency of this method in the sense that the posterior probability of the true model converges to one. When there are multiple groups of data available, instead of estimating the networks independently for each group, joint estimation of the networks may utilize the shared information among groups and lead to improved estimation for each individual network...
January 18, 2017: Biometrics
https://www.readbyqxmd.com/read/28099996/estimation-and-testing-problems-in-auditory-neuroscience-via-clustering
#3
Youngdeok Hwang, Samantha Wright, Bret M Hanlon
The processing of auditory information in neurons is an important area in neuroscience. We consider statistical analysis for an electrophysiological experiment related to this area. The recorded synaptic current responses from the experiment are observed as clusters, where the number of clusters is related to an important characteristic of the auditory system. This number is difficult to estimate visually because the clusters are blurred by biological variability. Using singular value decomposition and a Gaussian mixture model, we develop an estimator for the number of clusters...
January 18, 2017: Biometrics
https://www.readbyqxmd.com/read/28099993/conditional-estimation-in-two-stage-adaptive-designs
#4
Per Broberg, Frank Miller
We consider conditional estimation in two-stage sample size adjustable designs and the consequent bias. More specifically, we consider a design which permits raising the sample size when interim results look rather promising, and which retains the originally planned sample size when results look very promising. The estimation procedures reported comprise the unconditional maximum likelihood, the conditionally unbiased Rao-Blackwell estimator, the conditional median unbiased estimator, and the conditional maximum likelihood with and without bias correction...
January 18, 2017: Biometrics
https://www.readbyqxmd.com/read/28099992/on-estimation-of-time-dependent-attributable-fraction-from-population-based-case-control-studies
#5
Wei Zhao, Ying Qing Chen, Li Hsu
Population attributable fraction (PAF) is widely used to quantify the disease burden associated with a modifiable exposure in a population. It has been extended to a time-varying measure that provides additional information on when and how the exposure's impact varies over time for cohort studies. However, there is no estimation procedure for PAF using data that are collected from population-based case-control studies, which, because of time and cost efficiency, are commonly used for studying genetic and environmental risk factors of disease incidences...
January 18, 2017: Biometrics
https://www.readbyqxmd.com/read/28099991/bayescat-bayesian-co-estimation-of-alignment-and-tree
#6
Heejung Shim, Bret Larget
Traditionally, phylogeny and sequence alignment are estimated separately: first estimate a multiple sequence alignment and then infer a phylogeny based on the sequence alignment estimated in the previous step. However, uncertainty in the alignment is ignored, resulting, possibly, in overstated certainty in phylogeny estimates. We develop a joint model for co-estimating phylogeny and sequence alignment which improves estimates from the traditional approach by accounting for uncertainty in the alignment in phylogenetic inferences...
January 18, 2017: Biometrics
https://www.readbyqxmd.com/read/28099990/statistical-significance-for-hierarchical-clustering
#7
Patrick K Kimes, Yufeng Liu, David Neil Hayes, James Stephen Marron
Cluster analysis has proved to be an invaluable tool for the exploratory and unsupervised analysis of high-dimensional datasets. Among methods for clustering, hierarchical approaches have enjoyed substantial popularity in genomics and other fields for their ability to simultaneously uncover multiple layers of clustering structure. A critical and challenging question in cluster analysis is whether the identified clusters represent important underlying structure or are artifacts of natural sampling variation...
January 18, 2017: Biometrics
https://www.readbyqxmd.com/read/28085181/selection-of-effects-in-cox-frailty-models-by-regularization-methods
#8
Andreas Groll, Trevor Hastie, Gerhard Tutz
In all sorts of regression problems, it has become more and more important to deal with high-dimensional data with lots of potentially influential covariates. A possible solution is to apply estimation methods that aim at the detection of the relevant effect structure by using penalization methods. In this article, the effect structure in the Cox frailty model, which is the most widely used model that accounts for heterogeneity in survival data, is investigated. Since in survival models one has to account for possible variation of the effect strength over time the selection of the relevant features has to distinguish between several cases, covariates can have time-varying effects, time-constant effects, or be irrelevant...
January 13, 2017: Biometrics
https://www.readbyqxmd.com/read/28084017/estimation-of-the-relatedness-coefficients-from-biallelic-markers-application-in-plant-mating-designs
#9
Fabien Laporte, Alain Charcosset, Tristan Mary-Huard
The problem of inferring the relatedness distribution between two individuals from biallelic marker data is considered. This problem can be cast as an estimation task in a mixture model: at each marker the latent variable is the relatedness state, and the observed variable is the genotype of the two individuals. In this model, only the prior proportions are unknown, and can be obtained via ML estimation using the EM algorithm. When the markers are biallelic and the data unphased, the identifiability of the model is known not to be guaranteed...
January 12, 2017: Biometrics
https://www.readbyqxmd.com/read/28083872/a-space-time-skew-t-model-for-threshold-exceedances
#10
Samuel A Morris, Brian J Reich, Emeric Thibaud, Daniel Cooley
To assess the compliance of air quality regulations, the Environmental Protection Agency (EPA) must know if a site exceeds a pre-specified level. In the case of ozone, the level for compliance is fixed at 75 parts per billion, which is high, but not extreme at all locations. We present a new space-time model for threshold exceedances based on the skew-t process. Our method incorporates a random partition to permit long-distance asymptotic independence while allowing for sites that are near one another to be asymptotically dependent, and we incorporate thresholding to allow the tails of the data to speak for themselves...
January 12, 2017: Biometrics
https://www.readbyqxmd.com/read/28083869/bayesian-genome-and-epigenome-wide-association-studies-with-gene-level-dependence
#11
Eric F Lock, David B Dunson
High-throughput genetic and epigenetic data are often screened for associations with an observed phenotype. For example, one may wish to test hundreds of thousands of genetic variants, or DNA methylation sites, for an association with disease status. These genomic variables can naturally be grouped by the gene they encode, among other criteria. However, standard practice in such applications is independent screening with a universal correction for multiplicity. We propose a Bayesian approach in which the prior probability of an association for a given genomic variable depends on its gene, and the gene-specific probabilities are modeled nonparametrically...
January 12, 2017: Biometrics
https://www.readbyqxmd.com/read/28076654/estimating-varying-coefficients-for-partial-differential-equation-models
#12
Xinyu Zhang, Jiguo Cao, Raymond J Carroll
Partial differential equations (PDEs) are used to model complex dynamical systems in multiple dimensions, and their parameters often have important scientific interpretations. In some applications, PDE parameters are not constant but can change depending on the values of covariates, a feature that we call varying coefficients. We propose a parameter cascading method to estimate varying coefficients in PDE models from noisy data. Our estimates of the varying coefficients are shown to be consistent and asymptotically normally distributed...
January 11, 2017: Biometrics
https://www.readbyqxmd.com/read/28072468/a-multi-dimensional-functional-principal-components-analysis-of-eeg-data
#13
Kyle Hasenstab, Aaron Scheffler, Donatello Telesca, Catherine A Sugar, Shafali Jeste, Charlotte DiStefano, Damla Şentürk
The electroencephalography (EEG) data created in event-related potential (ERP) experiments have a complex high-dimensional structure. Each stimulus presentation, or trial, generates an ERP waveform which is an instance of functional data. The experiments are made up of sequences of multiple trials, resulting in longitudinal functional data and moreover, responses are recorded at multiple electrodes on the scalp, adding an electrode dimension. Traditional EEG analyses involve multiple simplifications of this structure to increase the signal-to-noise ratio, effectively collapsing the functional and longitudinal components by identifying key features of the ERPs and averaging them across trials...
January 10, 2017: Biometrics
https://www.readbyqxmd.com/read/28009454/direct-estimation-for-adaptive-treatment-length-policies-methods-and-application-to-evaluating-the-effect-of-delayed-peg-insertion
#14
Xin Lu, Brent A Johnson
Dysphagia is a primary cause of death among patients diagnosed with amyotrophic lateral sclerosis (ALS), and percutaneous endoscopic gastrostomy (PEG) is a procedure to insert a tube into the stomach to assist or replace oral feeding. It is believed that PEG is beneficial and, generally, earlier insertion is preferable to later. However, gathering clinical evidence to support these beliefs on the use and timing of PEG is challenging because controlled clinical trials are not feasible and clinical endpoints are confounded with PEG in observational data...
December 23, 2016: Biometrics
https://www.readbyqxmd.com/read/27959470/hypothesis-testing-of-matrix-graph-model-with-application-to-brain-connectivity-analysis
#15
Yin Xia, Lexin Li
Brain connectivity analysis is now at the foreground of neuroscience research. A connectivity network is characterized by a graph, where nodes represent neural elements such as neurons and brain regions, and links represent statistical dependence that is often encoded in terms of partial correlation. Such a graph is inferred from the matrix-valued neuroimaging data such as electroencephalography and functional magnetic resonance imaging. There have been a good number of successful proposals for sparse precision matrix estimation under normal or matrix normal distribution; however, this family of solutions does not offer a direct statistical significance quantification for the estimated links...
December 12, 2016: Biometrics
https://www.readbyqxmd.com/read/27936287/combining-item-response-theory-with-multiple-imputation-to-equate-health-assessment-questionnaires
#16
Chenyang Gu, Roee Gutman
The assessment of patients' functional status across the continuum of care requires a common patient assessment tool. However, assessment tools that are used in various health care settings differ and cannot be easily contrasted. For example, the Functional Independence Measure (FIM) is used to evaluate the functional status of patients who stay in inpatient rehabilitation facilities, the Minimum Data Set (MDS) is collected for all patients who stay in skilled nursing facilities, and the Outcome and Assessment Information Set (OASIS) is collected if they choose home health care provided by home health agencies...
December 9, 2016: Biometrics
https://www.readbyqxmd.com/read/27933633/discussion-of-a-risk-based-measure-of-time-varying-prognostic-discrimination-for-survival-models-by-c-jason-liang-and-patrick-j-heagerty
#17
Layla Parast, Carolyn M Rutter
No abstract text is available yet for this article.
December 8, 2016: Biometrics
https://www.readbyqxmd.com/read/27933613/rejoinder-to-discussions-on-a-risk-based-measure-of-time-varying-prognostic-discrimination-for-survival-models
#18
C Jason Liang, Patrick J Heagerty
No abstract text is available yet for this article.
December 8, 2016: Biometrics
https://www.readbyqxmd.com/read/27933612/discussion-of-a-risk-based-measure-of-time-varying-prognostic-discrimination-for-survival-models-by-c-jason-liang-and-patrick-j-heagerty
#19
H Michael, L Tian
No abstract text is available yet for this article.
December 8, 2016: Biometrics
https://www.readbyqxmd.com/read/27931085/discussion-of-a-risk-based-measure-of-time-varying-prognostic-discrimination-for-survival-models-by-c-jason-liang-and-patrick-j-heagerty
#20
Thomas Alexander Gerds, Martin Schumacher
No abstract text is available yet for this article.
December 8, 2016: Biometrics
journal
journal
23361
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"