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We consider an extension of linear mixed models by assuming a multivariate skew t distribution for the random effects and a multivariate t distribution for the error terms. The proposed model provides flexibility in capturing the effects of skewness and heavy tails simultaneously among continuous longitudinal data. We present an efficient alternating expectation-conditional maximization (AECM) algorithm for the computation of maximum likelihood estimates of parameters on the basis of two convenient hierarchical formulations. The techniques for the prediction of random effects and intermittent missing values under this model are also investigated. Our methodologies are illustrated through an application to schizophrenia data.
Department of Applied Mathematics, National Chung Hsing University, Taichung 402, Taiwan.
This article was published in the following journal.
Name: Biometrical journal. Biometrische Zeitschrift
HIV RNA viral load measures are often subjected to some upper and lower detection limits depending on the quantification assays. Hence, the responses are either left or right censored. Linear/nonlinea...
Childhood growth is a cornerstone of pediatric research. Statistical models need to consider individual trajectories to adequately describe growth outcomes. Specifically, well-defined longitudinal mod...
Repetitive manual handling tasks account for a substantial portion of work-related injuries. However, few studies report endurance time in repetitive manual handling tasks. Consequently, there is litt...
We present comprehensive derivations for the statistical models and methods for the use of pulsed gradient spin echo (PGSE) NMR to characterize the molecular weight distribution of polymers via the we...
Advanced methods for dose-response assessments are used to estimate the minimum concentrations of a nutrient that maximizes a given outcome of interest, thereby determining nutritional requirements fo...
Malaria is still endemic in the interior of French Guiana. mixed infections by 2 or more different malaria parasites lead to complex and potentially harmfull therapeutic problems. The aim ...
The purpose of this study is to evaluate the use and efficacy of the Encore Linear™ Hip System in a group of 200 patients for whom data has already been collected.
Background: Atherosclerotic carotid intima-media thickness (IMT) may be associated with alterations in the sensitivity of carotid and subclavian baroreceptors. Aim: The aim of this study ...
To compare serum ketone body (i.e., total ketones, β hydroxybutyrate, and estimate of acetoacetate) levels after single dose administration of AC-1204 mixed in water, AC-1202 mixed in wat...
In a randomized, cross-over designed study, the investigators examined the effectiveness of the carbohydrate counting method after consumption of mixed meals typical of the Greek cuisine w...
Statistical models in which the value of a parameter for a given value of a factor is assumed to be equal to a + bx, where a and b are constants. The models predict a linear regression.
Statistical models of the production, distribution, and consumption of goods and services, as well as of financial considerations. For the application of statistics to the testing and quantifying of economic theories MODELS, ECONOMETRIC is available.
Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.
Statistical formulations or analyses which, when applied to data and found to fit the data, are then used to verify the assumptions and parameters used in the analysis. Examples of statistical models are the linear model, binomial model, polynomial model, two-parameter model, etc.
Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.
Schizophrenia is a common serious long-term mental health condition that affects 5 in 1000 in the UK. It causes a range of different psychological symptoms; hallucinations, delusions, muddled thoughts based on the hallucinations or delusions and ch...
Psychiatry is the study of mental disorders and their diagnosis, management and prevention. Conditions include schizophrenia, severe depression and panic disorders among others. There are pharmaceutical treatments as well as other therapies to help...