1,721,378 research outputs found
Quantile regression in varying coefficient models: non-crossing quantile curves and heteroscedasticity
No full text© 2016, Springer-Verlag Berlin Heidelberg. Quantile regression is an important tool for describing the characteristics of conditional distributions. Population conditional quantile functions cannot cross for different quantile orders. Unfortunately estimated regression quantile curves often violate this and cross each other, which can be very annoying for interpretations and further analysis. In this paper we are concerned with flexible varying-coefficient modelling, and develop methods for quantile regression that ensure that the estimated quantile curves do not cross. A second aim of the paper is to allow for some heteroscedasticity in the error modelling, and to also estimate the associated variability function. We investigate the finite-sample performances of the discussed methods via simulation studies. Some applications to real data illustrate the use of the methods in practical settings.sponsorship: This research is supported by the IAP Research Network P7/06 of the Belgian State (Belgian Science Policy), and project GOA/12/014 of the Research Fund of the KU Leuven. The authors thank the Editor, an Associate Editor and the anonymous reviewers for their very valuable comments which led to a considerable improvement of the paper. (IAP Research Network of the Belgian State (Belgian Science Policy)|P7/06, Research Fund of the KU Leuven|GOA/12/014)status: Publishe
Unveiling spatial disparities: exploring high-risk diarhea among children under five using geographically weighted quantile regression
No full textAbstrak Penelitian ini menyelidiki pengaruh persentase akses air bersih, persentase kebiasaan mencuci tangan, dan kategorisasi toilet sehat pada kuantil atas risiko diare balita di Kota Bandung, Indonesia, menggunakan model Geographically Weighted Quantile Regression pada persentil ke-75 (τ = 0,75). Bandwidth optimal dipilih menggunakan validasi silang. Hasil penelitian menunjukkan bahwa signifikansi, kekuatan, dan arah hubungan antara diare dan faktor risikonya tergantung pada lokasinya. Pada kuantil atas τ = 0,75 Kecamatan Panyileukan diprediksi memiliki risiko diare tertinggi. Di kabupaten ini, ketiga prediktor berpengaruh signifikan terhadap risiko diare pada balita, dengan variabel persentase rumah yang mempraktikkan kebiasaan cuci tangan adalah variabel paling besar pengaruhnya dalam menurunkan risiko diare. Kesimpulannya, akses air bersih, kebiasaan cuci tangan, dan kategori toilet merupakan faktor risiko potensial terjadinya diare pada anak risiko tinggi. Metode GWQR memungkinkan pembuat keputusan untuk menangani masalah diare dengan tepat berdasarkan prediktor mana yang memiliki pengaruh besar pada daerah tertentu yang diminati. Selain itu, GWQR dapat digunakan untuk menyelidiki efek dari berbagai strategi intervensi dan secara efektif mengalokasikan sumber daya terbatas yang tersedia sesuai lokasi yang paling membutuhkannya. Abstract We investigate the impact of the percentage of clean water access, the percentage of handwashing habits, and the toilet category factors on the upper quantile of toddlers' diarrhea risks in Bandung City, Indonesia, using the Geographically Weighted Quantile Regression model on the 75th percentile (τ=0.75). The optimum bandwidth was selected using cross-validation. The results show that the significance, strength, and direction of the relationship between diarrhea and its risk factors depend on the location. At the upper quantile τ = 0.75, the Panyileukan district is predicted to have the highest diarrhea risk. In this district, all three predictors significantly affect the toddlers' diarrhea risk, with the variable of the percentage of houses practicing hand washing habits observed to reduce diarrhea risk the most. In conclusion, clean water access, handwashing habits, and toilet category are the potential risk factors for high-risk childhood diarrhea. This method is powerful as it would allow the decision-maker to handle the diarrhea problem aptly by focusing on the predictor that has a significant impact on a particular district of interest. And it can be used to investigate the effect of various intervention strategies and effectively allocate the limited available resources according to the most important locations
P-splines quantile regression estimation in varying coefficient models
No full textQuantile regression, as a generalization of median regression, has been widely used in statistical modeling. To allow for analyzing complex data situations, several flexible regression models have been introduced. Among these are the varying coefficient models, that differ from a classical linear regression model by the fact that the regression coefficients are no longer constant but functions that vary with the value taken by another variable, such as for example, time. In this paper, we study quantile regression in varying coefficient models for longitudinal data. The quantile function is modeled as a function of the covariates and the main task is to estimate the unknown regression coefficient functions. We approximate each coefficient function by means of P-splines. Theoretical properties of the estimators, such as rate of convergence and an asymptotic distribution are established. The estimation methodology requests solving an optimization problem that also involves a smoothing parameter. For a special case the optimization problem can be transformed into a linear programming problem for which then a Frisch–Newton interior point method is used, leading to a computationally fast and efficient procedure. Several data-driven choices of the smoothing parameters are briefly discussed, and their performances are illustrated in a simulation study. Some real data analysis demonstrates the use of the developed method.The authors are grateful to the Editor, Associate Editor and the referees for their very valuable comments on a first version of the paper. This research is supported by the IAP Research Network P7/06 of the Belgian State (Belgian Science Policy), and the projects GOA/07/04 and GOA/12/014 of the Research Fund of the KU Leuven
PENDEKATAN TAKTIS DALAM PEMBELAJARAN OLAHRAGA PERMAINAN HOKI (Penelitian Tindakan Kelas di SMA Laboratorium Percontohaan UPI)
Full text linkABSTRAK
Andriyana (050105). Skripsi ini berjudul “Pendekatan Taktis Dalam Pembelajaran Olahraga Permainan Hoki (penelitian tindakan kelas di SMA Laboratorium percontohan UPI)”. Penulisan skripsi ini di bawah bimbingan Drs. H. Toto Subroto M.Pd sebagai pembimbing I dan Carsiwan M.Pd sebagai Pembimbing II.
Penelitian ini di latar belakangi oleh masih kurang populernya olahraga hoki di kalangan masyarakat, khususnya di lingkungan sekolah menengah atas di kota bandung. Adapun masalah lain dalam penelitian ini adalah penerapan pendekatan taktis dalam pembelajaran aktivitas permainan hoki di SMA Laboratorium UPI. Rumusan masalah: apakah pendekatan taktis dapat meningkatkan pemahamaan bermain siswa SMA laboratorium UPI dalam pembelajaran aktivitas permainan hoki? Tujuan penelitian: “Ingin mengetahui apakah pendekatan taktis dapat meningkatkan pemahamaan bermain siswa SMA Laboratorium UPI dalam pembelajaran aktivitas permainan hoki?” Hipotesis tindakan: “Terdapat peningkatan pemahaman bermain Hoki siswa SMA Laboratorium UPI melalui model pendekatan taktis.” Metode penelitian adalah penelitian tindakan kelas. sampel penelitian ini siswa SMA laboratorium UPI yang mengikuti pembelajaran aktivitas permainan hoki.
Hasil penelitian menunjukan, melalui pendekatan taktis dalam pembelajaran aktivitas permainan hoki, maka kesalahan siswa dalam menggunakan pemahamaan pola-pola bermain dapat di minimalisir, serta kemampuan siswa dalam menggunakan pemahamaan pola-pola bermain hoki terdapat peningkatan dibandingkan sebelumnya, terbukti bahwa model pendekatan taktis memberikan pengaruh terhadap pemahaman bermain dalam pembelajaran aktivitas permainan hoki. Dengan demikian diharapkan kepada guru untuk menggunakan pendekatan taktis dalam pembelajaran aktivitas permainan hoki sebagai salah satu alternatif dalam mencapai tujuan
Quantile Regression in Space-Time Varying Coefficient Model of Upper Respiratory Tract Infections Data
No full textSpace-time varying coefficient models, which are used to identify the effects of covariates that change over time and spatial location, have been widely studied in recent years. One such model, called the quantile regression model, is particularly useful when dealing with outliers or non-standard conditional distributions in the data. However, when the functions of the covariates are not easily specified in a parametric manner, a nonparametric regression technique is often employed. One such technique is the use of B-splines, a nonparametric approach used to estimate the parameters of the unspecified functions in the model. B-splines smoothing has potential to overfit when the number of knots is increased, and thus, a penalty is added to the quantile objective function known as P-splines. The estimation procedure involves minimizing the quantile loss function using an LP-Problem technique. This method was applied to upper respiratory tract infection data in the city of Bandung, Indonesia, which were measured monthly across 30 districts. The results of the study indicate that there are differences in the effect of covariates between quantile levels for both space and time coefficients. The quantile curve estimates also demonstrate robustness with respect to outliers. However, the simultaneous estimation of the quantile curves produced estimates that were relatively close to one another, meaning that some quantile curves did not depict the actual data pattern as precisely. This suggests that each district in Bandung City not only has different categories of incidence rates but also has a heterogeneous incidence rate based on three quantile levels, due to the difference in the effects of covariates over time and space
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A Systematic Review of Quantile Regression in Varying Coefficient Models for Longitudinal Data
No full textVarying coefficient models have some regression coefficients allowed to vary as smooth functions of other variables. Applying varying coefficient models for longitudinal data determined the effect of different covariates between the time variable called the time-varying coefficient model. Several researchers used this model with a different approach. Quantile regression is a technique that uses P-splines as an estimation procedure. This research conducts a systematic literature review of the peer-reviewed papers on varying coefficient models with quantile objective function inspired by Hastie and Tibshirani. Furthermore, it shows a comprehensive bibliometric analysis involving a co-authorships network of the productive authors as well as a bibliometric map with the clustered term. The varying coefficient model and quantile regression are used to exposes a thematic analysis. Finally, the varying coefficient model, which includes time and spatial effects, is an interesting topic for further research.The authors are grateful for suggestions and inputs from the Rector of Universitas Padjadjaran
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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