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Maximum likelihood estimate

Nicolás M Ballarini, Gerd K Rosenkranz, Thomas Jaki, Franz König, Martin Posch
Identifying subgroups of treatment responders through the different phases of clinical trials has the potential to increase success in drug development. Recent developments in subgroup analysis consider subgroups that are defined in terms of the predicted individual treatment effect, i.e. the difference between the predicted outcome under treatment and the predicted outcome under control for each individual, which in turn may depend on multiple biomarkers. In this work, we study the properties of different modelling strategies to estimate the predicted individual treatment effect...
2018: PloS One
Yujing Sun, Mingliang Wang, Yuqiu Zhou, Lina Wang, Hui Zhang, Yumei Lv, Guohua Li
Schizophrenia is a debilitating, chronic, and high-refractory mental illness. Researchers should focus considerable attention to patients with mental disability. This study aims to explore the mediating effect of family function and medication adherence between symptoms and mental disability among Chinese patients with schizophrenia during the convalescent stage. Data from a cross-sectional sample of 499 Chinese patients with schizophrenia were used in this study. The participants were recruited and independently interviewed using the General Information Sheet, Positive and Negative Syndrome Scale (PANSS), World Health Organization Disability Assessment Schedule II (WHO-DAS II), Family APGAR Index (APGAR), and Morisky Medication Adherence Scale (MMAS-8) as outcome measures...
October 17, 2018: Psychology, Health & Medicine
Sytske Anne Bergstra, Lai-Ling Winchow, Elizabeth Murphy, Arvind Chopra, Karen Salomon-Escoto, João Eurico Fonseca, Cornelia F Allaart, Robert B M Landewé
OBJECTIVES: To compare consecutive disease modifying antirheumatic drug (DMARD)-treatment regimes in daily practice in patients with rheumatoid arthritis (RA) who failed on initial methotrexate, while using a multiple propensity score (PS) method to control for the spurious effects of confounding by indication. METHODS: Patients with newly diagnosed RA who had failed initial treatment with methotrexate were selected from METEOR, an international, observational registry...
October 16, 2018: Annals of the Rheumatic Diseases
Francesco Bartolucci, Alessio Farcomeni
A shared-parameter approach for jointly modeling longitudinal and survival data is proposed. With respect to available approaches, it allows for time-varying random effects that affect both the longitudinal and the survival processes. The distribution of these random effects is modeled according to a continuous-time hidden Markov chain so that transitions may occur at any time point. For maximum likelihood estimation, we propose an algorithm based on a discretization of time until censoring in an arbitrary number of time windows...
October 15, 2018: Statistics in Medicine
Zijian Li
Exploring better models for evaluating the distribution of pesticide residues in soil and sediment is necessary to assess and avoid population health risk. Frequentist philosophy and probability are widely used in many studies to apply a log-normal distribution associated with the maximum likelihood estimation, which assumes fixed parameters and relies on a large sample size for long-run frequency. However, frequentist probability might not be suitable for analyzing pesticide residue distribution, whose parameters are affected by many complex factors and should be treated as unfixed...
October 9, 2018: Environment International
Xiao-Chen Huang, Jin-Hui Su, Jie-Xiu Ouyang, Shan Ouyang, Chun-Hua Zhou, Xiao-Ping Wu
The Yangtze River Basin in China is one of the global hotspots of freshwater mussel (order Unionida) diversity with 68 nominal species. Few studies have tested the validity of these nominal species. Some taxa from the Yangtze unionid fauna have not been adequately examined using molecular data and well-positioned phylogenetically with respect to the global Unionida. We evaluated species boundaries of Chinese freshwater mussels, and disentangled their phylogenetic relationships within the context of the global freshwater mussels based on the multi-locus data and complete mitochondrial genomes...
October 8, 2018: Molecular Phylogenetics and Evolution
Alessandro Neri, Marco Carli, Federica Battisti
In this paper, a multi-resolution method for depth estimation from dense image arrays is presented. Recent progress in consumer electronics has enabled the development of low cost hand-held plenoptic cameras. In these systems, multiple views of a scene are captured in a single shot by means of a micro-lens array placed on the focal point of the first camera lens, in front of the imaging sensor. These views can be processed jointly to obtain accurate depth maps. In this contribution, to reduce the computational complexity associated to global optimization schemes based on match cost functions, we make a local estimate based on the maximization of the total log-likelihood spatial density aggregated along the epipolar lines corresponding to each view pair...
February 2019: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
Luca Mattioli, Antonio Canu, Daniela Passilongo, Massimo Scandura, Marco Apollonio
Background: Density estimation is a key issue in wildlife management but is particularly challenging and labour-intensive for elusive species. Recently developed approaches based on remotely collected data and capture-recapture models, though representing a valid alternative to more traditional methods, have found little application to species with limited morphological variation. We implemented a camera trap capture-recapture study to survey wolf packs in a 560-km2 area of Central Italy...
2018: Frontiers in Zoology
Sanku Dey, Fernando A Moala
This paper takes into account the estimation for the unknown parameters of the Gompertz distribution from the frequentist and Bayesian view points by using both objective and subjective prior distributions. We first derive non-informative priors using formal rules, such as Jefreys prior and maximal data information prior (MDIP), based on Fisher information and entropy, respectively. We also propose a prior distribution that incorporate the expert's knowledge about the issue under study. In this regard, we assume two independent gamma distributions for the parameters of the Gompertz distribution and it is employed for an elicitation process based on the predictive prior distribution by using Laplace approximation for integrals...
July 2018: Anais da Academia Brasileira de Ciências
Hassan S Bakouch
A new discrete distribution is introduced. The distribution involves the negative binomial and size biased negative binomial distributions as sub-models among others and it is a weighted version of the two parameter discrete Lindley distribution. The distribution has various interesting properties, such as bathtub shape hazard function along with increasing/decreasing hazard rate, positive skewness, symmetric behavior, and over- and under-dispersion. Moreover, it is self decomposable and infinitely divisible, which makes the proposed distribution well suited for count data modeling...
July 2018: Anais da Academia Brasileira de Ciências
Gauss M Cordeiro, Ahmed Z Afify, Haitham M Yousof, Selen Cakmakyapan, Gamze Ozel
We introduce a new three-parameter lifetime model called the Lindley Weibull distribution, which accommodates unimodal and bathtub, and a broad variety of monotone failure rates. We provide a comprehensive account of some of its mathematical properties including ordinary and incomplete moments, quantile and generating functions and order statistics. The new density function can be expressed as a linear combination of exponentiated Weibull densities. The maximum likelihood method is used to estimate the model parameters...
July 2018: Anais da Academia Brasileira de Ciências
Fernando A Peña-Ramírez, Renata R Guerra, Gauss M Cordeiro, Pedro R D Marinho
We propose a new lifetime model called the exponentiated power generalized Weibull (EPGW) distribution, which is obtained from the exponentiated family applied to the power generalized Weibull (PGW) distribution. It can also be derived from a power transform on an exponentiated Nadarajah-Haghighi random variable. Since several structural properties of the PGW distribution have not been studied, they can be obtained from those of the EPGW distribution. The model is very flexible for modeling all common types of hazard rate functions...
July 2018: Anais da Academia Brasileira de Ciências
Manuel Gomes, Rosalba Radice, Jose Camarena Brenes, Giampiero Marra
Missing not at random (MNAR) data pose key challenges for statistical inference because the substantive model of interest is typically not identifiable without imposing further (eg, distributional) assumptions. Selection models have been routinely used for handling MNAR by jointly modeling the outcome and selection variables and typically assuming that these follow a bivariate normal distribution. Recent studies have advocated parametric selection approaches, for example, estimated by multiple imputation and maximum likelihood, that are more robust to departures from the normality assumption compared with those assuming that nonresponse and outcome are jointly normally distributed...
October 8, 2018: Statistics in Medicine
Rachel Bastiaenen, Ilja M Nolte, Patricia B Munroe, Harriëtte Riese, Christopher Nelson, Henry O'Connor, Yi Gang, Helen R Warren, Claudia Cabrera, Wibke Reinhard, Christian Hengstenberg, Frühling V Rijsdijk, Tim Spector, Harold Snieder, Nilesh J Samani, Yalda Jamshidi, Elijah R Behr
BACKGROUND: Early repolarization (ER) is a risk marker for sudden cardiac death. Higher risk is associated with horizontal/descending ST-segment ER in the inferior or inferolateral ECG leads. Studies in family cohorts have demonstrated substantial heritability for the ER pattern, but genome-wide association studies (GWAS) have failed to identify statistically significant and replicable genetic signals. METHODS AND RESULTS: We assessed the narrow-sense and common single nucleotide polymorphism (SNP) heritability of ER and ER subtypes using ECG data from 5829 individuals (TwinsUK, BRIGHT and GRAPHIC cohorts)...
October 4, 2018: International Journal of Cardiology
Ling Xu, Zhuo Zhang, Qianxin Liu, Bin Zhou, Yinhua Liu, Qian Xiang, Sainan Zhu, Xuening Duan, Yimin Cui
Prognostic assessment after preoperative systemic therapy (PST) is critical to develop a therapeutic strategy for breast cancer management. Currently, a clinical-pathologic staging system that incorporates ER status and nuclear grading (CPS + EG), and the Neo-Bioscore system that includes HER2 status into CPS + EG, are used to predict outcomes in patients with breast cancer after PST. While HER2-positive is recognized as a favorable factor in the Neo-Bioscore system based on results in patients administered one year of trastuzumab as anti-HER2 therapy, most HER2-positive cases have difficulty accessing anti-HER2 treatment in China...
September 17, 2018: Thoracic Cancer
Maria Chatzou, Evan W Floden, Paolo Di Tommaso, Olivier Gascuel, Cedric Notredame
Phylogenetic reconstructions are essential in genomics data analyses and depend on accurate multiple sequence alignment (MSA) models. We show that all currently available large-scale progressive multiple alignment methods are numerically unstable when dealing with amino-acid sequences. They produce significantly different output when changing sequence input order. We used the HOMFAM protein sequences dataset to show that on datasets larger than 100 sequences, this instability affects on average 21.5% of the aligned residues...
March 29, 2018: Systematic Biology
William McIlhagga
Edge detection is widely believed to be an important early stage in human visual processing. However, there have been relatively few attempts to map human edge detection filters. In this study, observers had to locate a randomly placed step edge in brown noise (the integral of white noise) with a 1/f2 power spectrum. Their responses were modelled by assuming the probability the observer chose an edge location depended on the response of their own edge detection filter to that location. The observer's edge detection filter was then estimated by maximum likelihood methods...
October 10, 2018: Vision Research
Chengfeng Lei, Xiulian Sun
BACKGROUND: Evaluating the toxicity or effectiveness of two or more toxicants in a specific population often requires specialized statistical software to calculate and compare median lethal doses (LD50 s). Tests for equality of LD50 s using probit regression with parallel slopes have been implemented in many software packages, while tests for cases of arbitrary slopes are not generally available. METHODS: In this study, we established probit-log(dose) regression models and solved them by the maximum likelihood method using Microsoft Excel...
October 5, 2018: BMC Pharmacology & Toxicology
Xiongfeng Pan, Zhipeng Wang, Xiaoli Wu, Shi Wu Wen, Aizhong Liu
BACKGROUND: Studies investigating salivary cortisol level as susceptibility marker for post-traumatic stress disorder (PTSD) produced inconsistent results. The aim of this study was to compare salivary cortisol concentration levels in PTSD patients with those in controls by synthesizing published data. METHODS: We did a systematic review, meta-analysis and meta-regression of studies comparing concentrations of salivary cortisol between patients with PTSD and controls...
October 5, 2018: BMC Psychiatry
Dao Nguyen Vinh, Dang Thi Minh Ha, Nguyen Thi Hanh, Guy Thwaites, Maciej F Boni, Hannah E Clapham, Nguyen Thuy Thuong Thuong
BACKGROUND: The depletion of CD4 cell is the underlying reason for TB hyper-susceptibility among people with HIV. Consequently, the trend of TB dynamics is usually hidden by the HIV outbreak. METHODS: Here, we aim to evaluate the trend of TB dynamics quantitatively by a simple mathematical model using the known prevalence of hyper-susceptible individuals in the population. In order to estimate the parameters governing transmission we fit this model in a maximum likelihood framework to both reported TB cases and data from samples tested with Interferon Gamma Assay from Ho Chi Minh City - a city with high TB transmission and strong synchronization between HIV/AIDS and TB dynamics...
October 1, 2018: BMC Infectious Diseases
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