5,192 research outputs found
Model selection criteria and quadratic discrimination in ARMA and SETAR time series models
We show that analyzing model selection in ARMA time series models as a quadratic discrimination problem provides a unifying approach for deriving model selection criteria. Also this approach suggest a different definition of expected likelihood that the one proposed by Akaike. This approach leads to including a correction term in the criteria which does not modify their large sample performance but can produce significant improvement in the performance of the criteria in small samples. Thus we propose a family of criteria which generalizes the commonly used model selection criteria. These ideas can be extended to self exciting autoregressive models (SETAR) and we generalize the proposed approach for these non linear time series models. A Monte-Carlo study shows that this family improves the finite sample performance of criteria such as AIC, corrected AIC and BIC, for ARMA models, and AIC, corrected AIC, BIC and some cross-validation criteria for SETAR models. In particular, for small and medium sample size the frequency of selecting the true model improves for the consistent criteria and the root mean square error of prediction improves for the efficient criteria. These results are obtained for both linear ARMA models and SETAR models in which we assume that the threshold and the parameters are unknown
A Joint Dynamic Bi-Factor Model of the Yield Curve and the Economy as a Predictor of Business Cycles
This paper proposes an econometric model of the joint dynamic relationship between the yield curve and the economy to predict business cycles. We examine the predictive value of the yield curve to forecast both future economic growth as well as the beginning and end of economic recessions at the monthly frequency. The proposed multivariate dynamic factor model takes into account not only the popular term spread but also information extracted from the entire yield curve. The nonlinear model is used to investigate the interrelationship between the phases of the bond market and of the business cycle. The results indicate a strong interrelation between these two sectors. Although the popular term spread has a reasonable forecasting performance, the proposed factor model of the yield curve exhibits substantial incremental predictive value. This result holds in-sample and out-of-sample, using revised or real time unrevised data.Forecasting, Business Cycles, Yield Curve, Dynamic Factor Models, Markov Switching.
MODEL SELECTION CRITERIA AND QUADRATIC DISCRIMINATION IN ARMA AND SETAR TIME SERIES MODELS
We show that analyzing model selection in ARMA time series models as a quadratic discrimination problem provides a unifying approach for deriving model selection criteria. Also this approach suggest a different definition of expected likelihood that the one proposed by Akaike. This approach leads to including a correction term in the criteria which does not modify their large sample performance but can produce significant improvement in the performance of the criteria in small samples. Thus we propose a family of criteria which generalizes the commonly used model selection criteria. These ideas can be extended to self exciting autoregressive models (SETAR) and we generalize the proposed approach for these non linear time series models. A Monte-Carlo study shows that this family improves the finite sample performance of criteria such as AIC, corrected AIC and BIC, for ARMA models, and AIC, corrected AIC, BIC and some cross-validation criteria for SETAR models. In particular, for small and medium sample size the frequency of selecting the true model improves for the consistent criteria and the root mean square error of prediction improves for the efficient criteria. These results are obtained for both linear ARMA models and SETAR models in which we assume that the threshold and the parameters are unknown.
Predicting future reading problems based on pre-reading auditory measures: a longitudinal study of children with a familial risk of dyslexia
Purpose: This longitudinal study examines measures of temporal auditory processing
in pre-reading children with a family risk of dyslexia. Specifically, it attempts to
ascertain whether pre-reading auditory processing, speech perception, and phonological
awareness (PA) reliably predict later literacy achievement. Additionally, this study
retrospectively examines the presence of pre-reading auditory processing, speech
perception, and PA impairments in children later found to be literacy impaired.
Method: Forty-four pre-reading children with and without a family risk of dyslexia were
assessed at three time points (kindergarten, first, and second grade). Auditory processing
measures of rise time (RT) discrimination and frequency modulation (FM) along with
speech perception, PA, and various literacy tasks were assessed.
Results: Kindergarten RT uniquely contributed to growth in literacy in grades one and
two, even after controlling for letter knowledge and PA. Highly significant concurrent and
predictive correlations were observed with kindergarten RT significantly predicting first
grade PA. Retrospective analysis demonstrated atypical performance in RT and PA at all
three time points in children who later developed literacy impairments.
Conclusions: Although significant, kindergarten auditory processing contributions to
later literacy growth lack the power to be considered as a single-cause predictor; thus
results support temporal processing deficits’ contribution within a multiple deficit model
of dyslexia
Benefits of spatio-temporal modelling for short term wind power forecasting at both individual and aggregated levels
The share of wind energy in total installed power capacity has grown rapidly
in recent years around the world. Producing accurate and reliable forecasts of
wind power production, together with a quantification of the uncertainty, is
essential to optimally integrate wind energy into power systems. We build
spatio-temporal models for wind power generation and obtain full probabilistic
forecasts from 15 minutes to 5 hours ahead. Detailed analysis of the forecast
performances on the individual wind farms and aggregated wind power are
provided. We show that it is possible to improve the results of forecasting
aggregated wind power by utilizing spatio-temporal correlations among
individual wind farms. Furthermore, spatio-temporal models have the advantage
of being able to produce spatially out-of-sample forecasts. We evaluate the
predictions on a data set from wind farms in western Denmark and compare the
spatio-temporal model with an autoregressive model containing a common
autoregressive parameter for all wind farms, identifying the specific cases
when it is important to have a spatio-temporal model instead of a temporal one.
This case study demonstrates that it is possible to obtain fast and accurate
forecasts of wind power generation at wind farms where data is available, but
also at a larger portfolio including wind farms at new locations. The results
and the methodologies are relevant for wind power forecasts across the globe as
well as for spatial-temporal modelling in general
Changing the ideological roots of prejudice: Longitudinal effects of ethnic intergroup contact on social dominance orientation
Social Dominance Orientation (SDO) has been reported to be strongly related to a multitude of intergroup phenomena, but little is known about situational experiences that may influence SDO. Drawing from research on intergroup contact theory, we argue that positive intergroup contact is able to reduce SDO-levels. The results of an intergroup contact intervention study among high school students (Study 1, N=71) demonstrated that SDO-levels were indeed attenuated after the intervention. Furthermore, this intervention effect on SDO was especially pronounced among students reporting a higher quality of contact. A cross-lagged longitudinal survey among adults (Study 2, N=363) extended these findings by demonstrating that positive intergroup contact is able to decrease SDO over time. Moreover, we did not obtain evidence for the idea that people high in SDO would engage less in intergroup contact. These findings indicate that intergroup contact erodes one of the important socio-ideological bases of generalized prejudice and discrimination
Generalized Perceptual Linear Prediction (gPLP) Features for Animal Vocalization Analysis
A new feature extraction model, generalized perceptual linear prediction (gPLP), is developed to calculate a set of perceptually relevant features for digital signal analysis of animalvocalizations. The gPLP model is a generalized adaptation of the perceptual linear prediction model, popular in human speech processing, which incorporates perceptual information such as frequency warping and equal loudness normalization into the feature extraction process. Since such perceptual information is available for a number of animal species, this new approach integrates that information into a generalized model to extract perceptually relevant features for a particular species. To illustrate, qualitative and quantitative comparisons are made between the species-specific model, generalized perceptual linear prediction (gPLP), and the original PLP model using a set of vocalizations collected from captive African elephants (Loxodonta africana) and wild beluga whales (Delphinapterus leucas). The models that incorporate perceptional information outperform the original human-based models in both visualization and classification tasks
Beta-Product Poisson-Dirichlet Processes
Time series data may exhibit clustering over time and, in a multiple time
series context, the clustering behavior may differ across the series. This
paper is motivated by the Bayesian non--parametric modeling of the dependence
between the clustering structures and the distributions of different time
series. We follow a Dirichlet process mixture approach and introduce a new
class of multivariate dependent Dirichlet processes (DDP). The proposed DDP are
represented in terms of vector of stick-breaking processes with dependent
weights. The weights are beta random vectors that determine different and
dependent clustering effects along the dimension of the DDP vector. We discuss
some theoretical properties and provide an efficient Monte Carlo Markov Chain
algorithm for posterior computation. The effectiveness of the method is
illustrated with a simulation study and an application to the United States and
the European Union industrial production indexes
Analysis of Predictive Coding Models for Phonemic Representation Learning in Small Datasets
Neural network models using predictive coding are interesting from the
viewpoint of computational modelling of human language acquisition, where the
objective is to understand how linguistic units could be learned from speech
without any labels. Even though several promising predictive coding -based
learning algorithms have been proposed in the literature, it is currently
unclear how well they generalise to different languages and training dataset
sizes. In addition, despite that such models have shown to be effective
phonemic feature learners, it is unclear whether minimisation of the predictive
loss functions of these models also leads to optimal phoneme-like
representations. The present study investigates the behaviour of two predictive
coding models, Autoregressive Predictive Coding and Contrastive Predictive
Coding, in a phoneme discrimination task (ABX task) for two languages with
different dataset sizes. Our experiments show a strong correlation between the
autoregressive loss and the phoneme discrimination scores with the two
datasets. However, to our surprise, the CPC model shows rapid convergence
already after one pass over the training data, and, on average, its
representations outperform those of APC on both languages.Comment: 7 pages, 5 figures, 5 tables. Accepted paper at the workshop on
Self-supervision in Audio and Speech at ICML 202
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