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161.
Baptiste Gregorutti Bertrand Michel Philippe Saint-Pierre 《Statistics and Computing》2017,27(3):659-678
This paper is about variable selection with the random forests algorithm in presence of correlated predictors. In high-dimensional regression or classification frameworks, variable selection is a difficult task, that becomes even more challenging in the presence of highly correlated predictors. Firstly we provide a theoretical study of the permutation importance measure for an additive regression model. This allows us to describe how the correlation between predictors impacts the permutation importance. Our results motivate the use of the recursive feature elimination (RFE) algorithm for variable selection in this context. This algorithm recursively eliminates the variables using permutation importance measure as a ranking criterion. Next various simulation experiments illustrate the efficiency of the RFE algorithm for selecting a small number of variables together with a good prediction error. Finally, this selection algorithm is tested on the Landsat Satellite data from the UCI Machine Learning Repository. 相似文献
162.
The case study method has been essential in psychoanalysis and psychodynamic therapy, since it is the only way to describe and explore the deepest levels of the human psyche. Addiction is no more and no less than a particular psychological mechanism, identical at its core to other psychological compulsions, and is therefore best understood and reported by this method that explores the mind in depth. We will discuss the value of the case report method in general and in specific with regard to psychoanalysis and addiction, criticisms raised about this method, and comparisons of it with nomothetic research. 相似文献
163.
Natalia Khvorostianov Larissa Remennick 《Voluntas: International Journal of Voluntary and Nonprofit Organizations》2017,28(1):335-357
Recent immigrants seldom join the ranks of volunteers for various social causes. Immigrants from former socialist countries have been shown to be particularly averse to organized forms of volunteering for reasons rooted in their past, including forced forms of collectivism imposed by the state. In this qualitative study, we explored the perceptions and practices of volunteering among ex-Soviet immigrants (mostly educated middle-aged women) who ran a project for the benefit of elderly. Our findings show that most volunteers chose causes targeting fellow immigrants, their resettlement and well-being, and were motivated by the wish to build co-ethnic support network and overcome marginalization in the Israeli society. Other volunteers were driven by the need for self-actualization in the context of underemployment and occupational downgrading. Personal empowerment and higher identification with the receiving society were the most salient outcomes of volunteering for our informants. We conclude that for some immigrants, volunteering can serve as a strategy of social integration. 相似文献
164.
Nnamdi Ifeanyi Maduekwe Olufunmilayo O. Banjo Mike O. Sangodapo 《Social indicators research》2017,134(2):651-674
Civil Registration and Vital Statistics (CRVS) Systems are playing increasing roles in national and global data infrastructure, facilitating the achievement of key developmental goals. The performance of CRVS systems in many developing countries including Nigeria is sub optimal and information on their structure and operations scanty. This paper characterizes the statutory, institutional, and operational elements and social contexts of the Nigerian CRVS System. It includes a context analysis of the system and a review of improvement strategies and interventions. The paper shows that the Nigerian CRVS System is built on viable statutory and institutional platforms—the constitutional enshrinement of: universal, compulsory and continuous civil registration and, a central registration institution—the National Population Commission (NPC). NPC has registration hierarchy and infrastructure deployed at every level of political administration and mechanisms for efficient coordination of registration and production of vital statistics on live-births, deaths and stillbirths amongst other vital events. The major weaknesses of the system include inadequate financing and deployment of registration facilities, conflicting statutes and institutional arrangements for the registration of key events like death and stillbirths. Other weaknesses include intra-organizational conflicts in resource allocation and weak ICT infrastructure within the NPC. These are compounded by overarching contextual issues namely registration unfriendly sociocultural norms, weak national data infrastructure, systemic corruption, poverty and undeveloped civic culture. Domestic initiatives and interventions to improve the system have focused on birth registration, while multilateral interventions have only made a modest impact on the system. Thus, holistic in-country improvement initiatives supported with robust interventions are imperative to overcome weaknesses in the Nigerian CRVS system. However fundamental improvements in CRVS systems in developing countries like Nigeria may likely only follow sustainable solutions to overarching contextual issues especially poor infrastructure, weak institutions, poverty and systemic corruption. 相似文献
165.
Inference of interaction networks represented by systems of differential equations is a challenging problem in many scientific disciplines. In the present article, we follow a semi-mechanistic modelling approach based on gradient matching. We investigate the extent to which key factors, including the kinetic model, statistical formulation and numerical methods, impact upon performance at network reconstruction. We emphasize general lessons for computational statisticians when faced with the challenge of model selection, and we assess the accuracy of various alternative paradigms, including recent widely applicable information criteria and different numerical procedures for approximating Bayes factors. We conduct the comparative evaluation with a novel inferential pipeline that systematically disambiguates confounding factors via an ANOVA scheme. 相似文献
166.
We examine the effect of anomalous temperatures, rainfall levels, and monsoon timing on migration outcomes in Indonesia. Using panel data from the Indonesian Family Life Survey and high-resolution climate data, we assess whether intra- and inter-province moves are used as a response to climatic shocks. We evaluate the relative importance of temperature, rainfall, and monsoon timing for migration. Only temperature and monsoon timing have significant effects, and these do not operate in the direction commonly assumed. Estimated effects vary according to individuals’ gender, membership in a farm household, and location. We also analyze climate effects on sources of household income, which highlights the multi-phasic nature of household responses. Results undermine narratives of a uniform global migratory response to climate change and highlight the heterogeneous use of migration as a response to such changes. By extending previous research on environmentally induced migration in Indonesia, we also highlight the sensitivity of estimates to alternative climate and migration measures. 相似文献
167.
Arnd Albrecht 《Gruppendynamik und Organisationsberatung》2017,48(3):185-192
Organizations are driven by continuous change. Global, socio-economic and technological megatrends – demographic changes and digitalization – are the reasons for transformation. Traditional organization forms are not in line with customers‘ need. Disruptive modes of development and innovations have been intensively discussed elsewhere. The topic of disruptive organization have not been discussed towards internal and external customer relations, although of high relevance. 129 Managers answered on communication ways and the purpose of upcoming meaning for the working place/office. Two new models and five concrete recommendations have been established for upcoming future organization. 相似文献
168.
Competing risks occur in a time-to-event analysis in which a patient can experience one of several types of events. Traditional methods for handling competing risks data presuppose one censoring process, which is assumed to be independent. In a controlled clinical trial, censoring can occur for several reasons: some independent, others dependent. We propose an estimator of the cumulative incidence function in the presence of both independent and dependent censoring mechanisms. We rely on semi-parametric theory to derive an augmented inverse probability of censoring weighted (AIPCW) estimator. We demonstrate the efficiency gained when using the AIPCW estimator compared to a non-augmented estimator via simulations. We then apply our method to evaluate the safety and efficacy of three anti-HIV regimens in a randomized trial conducted by the AIDS Clinical Trial Group, ACTG A5095. 相似文献
169.
The use of Bayesian nonparametrics models has increased rapidly over the last few decades driven by increasing computational power and the development of efficient Markov chain Monte Carlo algorithms. We review some applications of these models in economic applications including: volatility modelling (using both stochastic volatility models and GARCH-type models) with Dirichlet process mixture models, uses in portfolio allocation problems, long memory models with flexible forms of time-dependence, flexible extension of the dynamic Nelson-Siegel model for interest rate yields and multivariate time series models used in macroeconometrics. 相似文献
170.
In this paper, we study space–time generalized additive models. We apply the penalyzed likelihood method to fit generalized additive models (GAMs) for nonseparable spatio-temporal correlated data in order to improve the estimation of the response and smooth terms of GAMs. The results show that our space–time generalized additive models estimated response and smooth terms reasonable well, and in addition, the mean squared error, mean absolute deviation and coverage intervals improved considerably compared to the classic GAM. An application on particulate matter concentration in the North-Italian region of Piemonte is also presented. 相似文献