Robust Model Selection in Dynamic Models with an Application to Comparing Predictive Accuracy

A model selection procedure based on a general criterion function, with an example of the Kullback-Leibler Information Criterion (KLIC) using quasi-likelihood functions, is considered for dynamic non-nested models. We propose a robust test which generalizes Lien and Vuong's (1987) test with a Heteroscadasticity/Autocorrelation Consistent (HAC) variance estimator. We use the fixed-b asymptotics developed in Kiefer and Vogelsang (2005) to improve the asymptotic approximation to the sampling distribution of the test statistic. The fixed-b approach is compared with a bootstrap method and the standard normal approximation in Monte Carlo simulations. The fixed-b asymptotics and the bootstrap method are found to be markedly superior to the standard normal approximation. An empirical application for foreign exchange rate forecasting models is presented.

Geometry of the Log-Likelihood Ratio Statistic in Misspecified Models

We show that the asymptotic mean of the log-likelihood ratio in a misspecified model is a differential geometric quantity that is related to the exponential curvature of Efron (1978), Amari (1982), and the preferred point geometry of Critchley et al. (1993, 1994). The mean is invariant with respect to reparametrization, which leads to the differential geometrical approach where coordinate-system invariant quantities like statistical curvatures play an important role. When models are misspecified, the likelihood ratios do not have the chi-squared asymptotic limit, and the asymptotic mean of the likelihood ratio depends on two geometric factors, the departure of models from exponential families (i.e. the exponential curvature) and the departure of embedding spaces from being totally flat in the sense of Critchley et al. (1994). As a special case, the mean becomes the mean of the usual chi-squared limit (i.e. the half of the degrees of freedom) when these two curvatures vanish. The effect of curvatures is shown in the non-nested hypothesis testing approach of Vuong (1989), and we correct the numerator of the test statistic with an estimated asymptotic mean of the log-likelihood ratio to improve the asymptotic approximation to the sampling distribution of the test statistic.

Development and Validation of Credit-Scoring Models

Accurate credit-granting decisions are crucial to the efficiency of the decentralized capital allocation mechanisms in modern market economies. Credit bureaus and many .nancial institutions have developed and used credit-scoring models to standardize and automate, to the extent possible, credit decisions. We build credit scoring models for bankcard markets using the Office of the Comptroller of the Currency, Risk Analysis Division (OCC/RAD) consumer credit database (CCDB). This unusu- ally rich data set allows us to evaluate a number of methods in common practice. We introduce, estimate, and validate our models, using both out-of-sample contempora- neous and future validation data sets. Model performance is compared using both separation and accuracy measures. A vendor-developed generic bureau-based score is also included in the model performance comparisons. Our results indicate that current industry practices, when carefully applied, can produce models that robustly rank-order potential borrowers both at the time of development and through the near future. However, these same methodologies are likely to fail when the the objective is to accurately estimate future rates of delinquency or probabilities of default for individual or groups of borrowers.

Building Framework For Smart And Integrated Water Management System Operation For The Bandung Metropolitan, Indonesia

The Citarum River Basin (CRB) is located in the West Java Province of Indonesia and covers 13,000 km2 lying immediately to the east of Jabodetabek conurbation. The CRB, as an important national strategic river basin, is the heart of the rapid and sustainable economic growth of the nation toward ‘Green Everlasting Indonesia’. However, rapid increase in population and industrialization in the Bandung Metropolitan and surrounding upstream area of the CRB has been accelerating serious water scarcity, river pollution, and flood damage. In order to solve these complex and complicated water management issues in the rapidly developing mega city, intensive and integrated efforts for reshaping urban and basin water management model are urgently required. As part of these efforts, a cooperative project between Indonesia and Korea has recently initiated to develop new dam(s) and integrated water infrastructure management system in the upper CRB. This paper introduces the main concept and approach of this combined structural (new dams) and non-structural (integrated dams operating system of existing and new dams) measures and on-going development practice. The project will contribute not only for securing necessary water and hydro energy for the people in Bandung mega city but also for adapting and mitigating the increasing risk from climate change in the region

Mucosal and salivary microbiota associated with recurrent aphthous stomatitis

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.Abstract Background Recurrent aphthous stomatitis (RAS) is a common oral mucosal disorder of unclear etiopathogenesis. Although recent studies of the oral microbiota by high-throughput sequencing of 16S rRNA genes have suggested that imbalances in the oral microbiota may contribute to the etiopathogenesis of RAS, no specific bacterial species associated with RAS have been identified. The present study aimed to characterize the microbiota in the oral mucosa and saliva of RAS patients in comparison with control subjects at the species level. Results The bacterial communities of the oral mucosa and saliva from RAS patients with active lesions (RAS, n = 18 for mucosa and n = 8 for saliva) and control subjects (n = 18 for mucosa and n = 7 for saliva) were analyzed by pyrosequencing of the 16S rRNA genes. There were no significant differences in the alpha diversity between the controls and the RAS, but the mucosal microbiota of the RAS patients showed increased inter-subject variability. A comparison of the relative abundance of each taxon revealed decreases in the members of healthy core microbiota but increases of rare species in the mucosal and salivary microbiota of RAS patients. Particularly, decreased Streptococcus salivarius and increased Acinetobacter johnsonii in the mucosa were associated with RAS risk. A dysbiosis index, which was developed using the relative abundance of A. johnsonii and S. salivarius and the regression coefficients, correctly predicted 83 % of the total cases for the absence or presence of RAS. Interestingly, A. johnsonii substantially inhibited the proliferation of gingival epithelial cells and showed greater cytotoxicity against the gingival epithelial cells than S. salivarius. Conclusion RAS is associated with dysbiosis of the mucosal and salivary microbiota, and two species associated with RAS have been identified. This knowledge may provide a diagnostic tool and new targets for therapeutics for RAS

Fibroblastic Type Osteosarcoma of the Ulna: a Case Report of a Tumor in a Rare Location with Atypical Imaging Findings

The ulna is a rare site of origin for osteosarcoma, and purely osteolytic osteosarcomas are uncommonly noted on conventional radiographs. We present a patient with a lytic lesion of the distal ulna for which imaging findings suggested an aneurysmal bone cyst. The lesion was histologically confirmed to be a fibroblastic osteosarcoma

Epidemiologic survey of head and neck cancers in Korea.

Head and neck cancers have never been systematically studied for clinical purposes yet in Korea. This epidemiological survey on head and neck cancer patients was undertaken from January to December 2001 in 79 otorhinolaryngology resident-training hospitals nationwide. The number of head and neck cancer patients was 1,063 cases in the year. The largest proportion of cases arose in the larynx, as many as 488 cases, which accounted for 45.9%. It was followed by, in order of frequency, oral cavity (16.5%), oropharynx (10.0%), and hypopharynx (9.5%). The male:female ratio was 5:1, and the mean age was 60.3 yr. Surgery was the predominant treatment modality in head and neck cancers: 204 (21.5%) cases were treated with only surgery, 198 (20.8%) cases were treated with surgery and radiotherapy, 207 cases (21.8%) were treated with combined therapy of surgery, radiotherapy, and chemotherapy. Larynx and hypopharynx cancers had a stronger relationship with smoking and alcohol drinking than other primary site cancers. Of them, 21 cases were found to be metastasized at the time of diagnosis into the lung, gastrointestinal tract, bone, or brain. Coexisting second primary malignancies were found in 23 cases. At the time of diagnosis, a total of 354 cases had cervical lymph node metastasis accounting for 42.0%