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X-WR-CALNAME:Institute of Mathematics and Informatics
X-ORIGINAL-URL:https://math.bas.bg
X-WR-CALDESC:Събития за Institute of Mathematics and Informatics
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DTSTART:20220327T010000
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DTSTART;TZID=Europe/Sofia:20220629T140000
DTEND;TZID=Europe/Sofia:20220629T153000
DTSTAMP:20260622T194649
CREATED:20220623T160023Z
LAST-MODIFIED:20220623T160023Z
UID:12571-1656511200-1656516600@math.bas.bg
SUMMARY:Национален семинар по стохастика
DESCRIPTION:Поредната сбирка на \nНационалния семинар по стохастика\nще се проведе на 29 юни 2022 г. (сряда) от 14:00 часа в зала 503 на ИМИ – БАН. \nДоклад на тема \nModelling longitudinal cognitive test data with ceiling effects and left skewness\nще изнесе \nДеница Григорова (ФМИ – СУ)\, съвместна работа с Деян Палежев и Ралица Георгиева. \nАбстракт: Cognitive tests are among the markers for the development of cognitive diseases such as Alzheimer’s disease. We model the scores from the Mini Mental State Examination (MMSE) over time on data from the Alzheimer’s Disease Neuroimaging Initiative studies (ADNI\, http://adni.loni.usc.edu/). The challenge of modelling such an outcome is that the data are left-skewed with ceiling effects – the maximum possible score on the MMSE is 30 and this maximum is often achieved by healthy individuals. Different approaches have been considered in the statistical literature\, such as linear mixed effects models on transformed data\, mixture models based on latent class growth analysis and generalized additive models for location\, scale and shape (GAMLSS). We apply the binomial and beta-binomial GAMLSS specifications because they allow to account for the features of the data. We use non-parametric random effects to model correlations among repeated measures on the same individual and maximum likelihood for estimation and inference. We propose a bootstrap method for estimation of the covariance matrix of the estimates needed for hypothesis testing involving more than one regression coefficient. Finally\, we perform simulation studies to compare the estimation procedure implemented in the gamlss R package under different scenarios.
URL:https://math.bas.bg/event/%d0%bd%d0%b0%d1%86%d0%b8%d0%be%d0%bd%d0%b0%d0%bb%d0%b5%d0%bd-%d1%81%d0%b5%d0%bc%d0%b8%d0%bd%d0%b0%d1%80-%d0%bf%d0%be-%d1%81%d1%82%d0%be%d1%85%d0%b0%d1%81%d1%82%d0%b8%d0%ba%d0%b0-31/
LOCATION:Институт по математика и информатика – БАН\, Block 8\, 1113 БАН IV км.\, София\, Bulgaria
CATEGORIES:Редовен семинар
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