Search results for "Statistica"

Determining the Number of Factors to Retain in EFA: An easy-to-use computer program for carrying out Parallel Analysis

2007

Parallel Analysis is a Monte Carlo simulation technique that aids researchers in determining the number of factors to retain in Principal Component and Exploratory Factor Analysis. This method provides a superior alternative to other techniques that are commonly used for the same purpose, such as the Scree test or the Kaiser's eigenvalue-greater-than-one rule. Nevertheless, Parallel Analysis is not well known among researchers, in part because it is not included as an analysis option in the most popular statistical packages. This paper describes and illustrates how to apply Parallel Analysis with an easy-to-use computer program called ViSta-PARAN. ViSta-PARAN is a user-friendly application …

Lead Excretion in Spanish Children with Autism Spectrum Disorder

2015

Among epigenetic factors leading to increased prevalence of juvenile neuropsychiatric disorders, including autism spectrum disorder, exposure to metals, such as lead (Pb) have led to conflicting results. The aim of the present study was to determine the levels of Pb in the urine of children with autism spectrum disorder (ASD) compared with typically developing children (TD) age- and sex-matched, and to analyze any association between core symptoms of ASD, special diets, supplements intake or prescription drugs and the concentration of Pb. The study was performed in a group of children with ASD (n = 35, average age 7.4 ± 0.5 years) and TD (n = 34, average age 7.7 ± 0.9 years). Measurement of…

LASSO regression via smooth L1-norm approximation

2010

This paper discusses estimation of regression model with LASSO penalty when the L1-norm is replaced with its parametric smooth approximation. The resulting parameter estimators are more manageable than those from standard LASSO, standard errors are easy computed via a sandwich formula, and the model degrees of freedom may be computed straightforwardly. Moreover the resulting objective function may be minimized using usual optimization algorithms for regular models, for instance Newton-Raphson or iterative least squares.

Spectroscopic and Structural Investigation of the Confinement of D and L Dimethyl Tartrate in Lecithin Reverse Micelles

2009

The confinement of D and L dimethyl tartrate in lecithin reverse micelles dispersed in cyclohexane has been investigated by FT-IR, polarimetry, electronic and vibrational circular dichroism (ECD and VCD), 1H NMR, and small-angle X-ray scattering (SAXS). Measurements have been performed at room temperature as a function of the solubilizate-to-surfactant molar ratio (R) at fixed lecithin concentration. The analysis of experimental data indicates that the dimethyl tartrate molecules are solubilized within reverse micelles in proximity to the surfactant head groups in the same way for the D and L forms. The encapsulation of dimethyl tatrate within lecithin reverse micelles involves changes in i…

Refugees’ perception of their new life in Germany

2021

Since 2015, Germany has been hosting noticeable incoming flows of refugees and asylum seekers and despite the quality of life of refugees is expected to be improved in the aftermath of their arrival to Germany, refugees are still facing several problems of integration and economic deprivation. Using a sample of individuals from the first wave of the German IAB-BAMF-SOEP Survey of Refugees, we present some preliminary analyses on their life satisfaction (LS). A gamma glm was estimated to focus on the association among levels of LS and main socio-demographic characteristics as well as post-migration factors. Greater stability (both in the legal and personal sphere) in refugees’ lives is posit…

Transition to Digital Distribution Platforms and Business Model Evolution

2019

How do business models evolve when technology-based firms move from physical distribution channels to digital distribution platforms? This is an important question, since digitalization of distribution platforms provides new opportunities to expand the reach and customer base of technology-based firms. Based on an in-depth multi-case study of four Japanese high-tech firms, we seek to expand our understanding of digital transformation and business model literature. Our findings indicate that that through digital transformation, the case firms’ business models evolved toward more constant interaction with the market, in particular through digital platforms. This interaction includes growing a…

Locked-in Syndrome and 18F-fluorodeoxyglucose-positron Emission Tomography/Computed Tomography: Observations from a Case of Basilar Artery Thrombosis

2018

We report the case of a 59-year-old male patient suffering from locked-in syndrome (LIS) following basilar artery thrombosis despite an attempt of thrombolysis. Neurological examination showed quadriplegia and aphonia and a state of coma requiring mechanical ventilation was diagnosed. The use of 18F-fluorodeoxyglucose (18F-FDG)-positron emission tomography (PET) allowed to detect a normal 18F-FDG uptake in the main cerebral cortical areas and a significant reduction of 18F-FDG uptake in both cerebellar hemispheres, compatible with a functional deafferentation, helping confirming the clinical suspicion of LIS. The diagnosis of LIS, according to literature, is based on the clinical assessment…

Book Review: Statistical Inference as Severe Testing

2019

Estimating the Bayesian posterior distribution of indirect effects in causal longitudinal mediation analysis

Many research studies aim to unveil the causal mechanism underlying a particular phenomenon; mediation analysis is increasingly used for this scope, and longitudinal data are particularly suited for mediation since they ensure the correct temporal order among variables and the time spanning allows the causal effects to unfold. This explains the rise of interest in the topic of longitudinal mediation analysis. Many approaches have been proposed to cope with longitudinal mediation (Fosen et al., 2005; Lin et al., 2017), among which mixed-effect modelling. In a recent paper, Bind et al. (Biostatistics, 2016) made use of generalised mixed effect models and provided conditions for the identifiab…

Bayesian causal mediation analysis through linear mixed-effect models

2022

In mediational settings, the main focus is on the estimation of the indirect effect of an exposure on an outcome through a third variable called mediator. The traditional maximum likelihood estimation method presents several problems in the estimation of the standard error and the confidence interval of the indirect effect. In this paper, we propose a Bayesian approach to obtain the posterior distribution of the indirect effect through MCMC, in the context of mediational mixed models for longitudinal data. A simulation study shows that our method outperforms the traditional maximum likelihood approach in terms of bias and coverage rates.