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Target Variable (target + variable)
Selected AbstractsOPTIMAL FORECAST COMBINATION UNDER REGIME SWITCHING*INTERNATIONAL ECONOMIC REVIEW, Issue 4 2005Graham Elliott This article proposes a new forecast combination method that lets the combination weights be driven by regime switching in a latent state variable. An empirical application that combines forecasts from survey data and time series models finds that the proposed regime switching combination scheme performs well for a variety of macroeconomic variables. Monte Carlo simulations shed light on the type of data-generating processes for which the proposed combination method can be expected to perform better than a range of alternative combination schemes. Finally, we show how time variations in the combination weights arise when the target variable and the predictors share a common factor structure driven by a hidden Markov process. [source] Core Inflation and Monetary PolicyINTERNATIONAL FINANCE, Issue 3 2001Marianne Nessén What are the implications of targeting different measures of inflation? We extend a basic theoretical framework of optimal monetary policy under inflation targeting (Svensson 1997) to include several components of CPI inflation, and analyse the implications of using different measures of inflation as the target variable , headline CPI inflation, core inflation, and CPI excluding interest rates. Our main results are the following. First, barring the interest rate component, temporary shocks to inflation do not affect optimal monetary policy under any regime. Second, indirect (second-round) effects of disturbances on target variables need to be accounted for properly. Simply excluding seemingly temporary disturbances from the reaction function risks leading to inappropriate policy responses. Third, it may be optimal to respond to changes in one measure of inflation even if the target is defined in terms of another. Fourth, the presence of the direct interest rate component in the CPI tends to push optimal monetary policy in an expansionary direction. The net effect, considering also the traditional channel, however, depends on the nature of the initial disturbance. [source] Decision trees with optimal joint partitioningINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 7 2005Djamel A. Zighed Decision tree methods generally suppose that the number of categories of the attribute to be predicted is fixed. Breiman et al., with their Twoing criterion in CART, considered gathering the categories of the predicted attribute into two supermodalities. In this article, we propose an extension of this method. We try to merge the categories in an optimal unspecified number of supermodalities. Our method, called Arbogodaï, allows during tree growing for grouping categories of the target variable as well as categories of the predictive attributes. It handles both categorical and quantitative attributes. At the end, the user can choose to generate either a set of single rules or a set of multiconclusion rules that provide interval-like predictions. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 693,718, 2005. [source] Age of onset has limited association with body mass index at time of presentation for anorexia nervosa: Comparison of peak-onset and late-onset anorexia nervosa groupsPSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 6 2007HIROYUKI KIMURA md Abstract The clinical characteristics differentiating late-onset anorexia nervosa (AN) from typical pubertal onset AN remain unclear. The purpose of the present study was to examine these differences in a retrospective analysis. A total of 149 female AN patients was divided into two groups: a peak-onset AN group (n = 125) in which onset occurred between the ages of 15 and 24 years, and a late-onset AN group (n = 24) in which onset occurred at the age of ,25 years. A logistic regression analysis was conducted with this classification as the target variable and five clinical factors as explanatory variables for the clinical characteristics at the time of initial examination. Body mass index (BMI) at the time of presentation was identified as a possible factor affecting classification as peak-onset or late-onset AN. In addition, a negative linear correlation was detected between age of onset and BMI at the time of initial examination. The results suggest that BMI at the time of the initial examination is an important clinical characteristic to differentiate peak-onset AN and late-onset AN. [source] Alpha-dihydroergocryptine in the treatment of de novo parkinsonian patients: results ofa multicentre, randomized, double-blind, placebo-controlled studyACTA NEUROLOGICA SCANDINAVICA, Issue 6 2000B. Bergamasco Introduction, A multicentre, randomized, double-blind, placebo-controlled, parallel group study was carried out in 123 patients suffering from never treated (de novo) idiopathic Parkinson's disease (PD). The aim of the study was to confirm the efficiency and safety of ,-dihydroergocryptine (,-DHEC) given as monotherapy in the symptomatic treatment of PD. The total score of the Unified Parkinson's Disease Rating Scale (UPDRS) was identified as the efficacy target variable. Patients and methods, Sixty-two patients (32 males, 30 females, mean age±SD 64±10) were randomized to ,-dihydroergocryptine and 61 (30 males, 31 females, mean age 63.8±9.1) to placebo. According to the experimental design, a 18-month double-blind phase vs placebo was followed. Two interim analyses were planned both at the 3rd and 12th month of treatment, in order to avoid continuation on placebo, if clear differences between groups were found (stopping criterium: nominal significance level equal to 0.022 in the analysis of the target variable). Analysis of variance was performed both on the per protocol (PP) and intent-to-treat (ITT) sample. Results, The results on the first interim analysis showed significant differences between treatment groups of the UPDRS total score both in the ITT (115 patients, ,-DHEC: No. 56; placebo: No. 59; P=0.019) and PP (96 patients, ,-DHEC: No. 46; placebo: No. 50; P=0.001) sample, why the trial was stopped. At the time of stopping the trial, 73 patients (,-DHEC: No. 37; placebo: No. 36) had reached the 6-month observation visit; the analysis carried out on this subset of patients confirmed the efficacy of ,-dihydroergocryptine in early PD and the correctness of the decision to stop. The incidence of adverse drug reactions (ADR) did not differ between ,-dihydroergocryptine and placebo recipients, gastrointestinal complaints being the most frequent. Conclusion, The results indicate that ,-dihydroergocryptine is safe and effective in improving symptoms of de novo parkinsonian patients. [source] L -Lysine Monohydrochloride Syrup Concentration using a Membrane Hybrid Process of Ultrafiltration and Vacuum Membrane DistillationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2008O. Bakhtiari Abstract The development of energy saving membrane separation processes is finding a unique position in process industries. One of the important areas where they are employed is the biotechnology industry. This industry has its own specifications and requirements, e.g., levels of diluteness, thermal, chemical and shear fragility. Membrane separation processes have the characteristics necessary to match these specifications and needs. In this research, the determination of the experimental concentration of L -Lysine monohydrochloride (L -lysine-HCl) syrup was investigated using ultrafiltration (UF) and vacuum membrane distillation (VMD) hybrid membrane processes. Four parameters that are known to have significant influence on the UF process were examined, i.e., pressure difference across the membrane, feed concentration of L -lysine-HCl, feed velocity on the membrane surface, and pH. For the VMD unit, pressure difference and pH were replaced with feed temperature and vacuum pressure on the permeate side of membrane. Each process was carried out separately and the results were used to design a bench-scale process. In order to save time and money, the Taguchi method of experimental design was employed. The effects of feed concentration, pressure difference across the membrane, feed velocity on the membrane surface, and pH on the target variable, i.e., the membrane flux, in the UF process were 39.93, 38.65, 9.36, and 9.59,%, respectively. For the VMD process, these values were 64.79, 22.16, 6.21, and 2.14,% for feed temperature, feed concentration, vacuum pressure on the permeate side, and feed velocity on the membrane surface, respectively. [source] Core Inflation and Monetary PolicyINTERNATIONAL FINANCE, Issue 3 2001Marianne Nessén What are the implications of targeting different measures of inflation? We extend a basic theoretical framework of optimal monetary policy under inflation targeting (Svensson 1997) to include several components of CPI inflation, and analyse the implications of using different measures of inflation as the target variable , headline CPI inflation, core inflation, and CPI excluding interest rates. Our main results are the following. First, barring the interest rate component, temporary shocks to inflation do not affect optimal monetary policy under any regime. Second, indirect (second-round) effects of disturbances on target variables need to be accounted for properly. Simply excluding seemingly temporary disturbances from the reaction function risks leading to inappropriate policy responses. Third, it may be optimal to respond to changes in one measure of inflation even if the target is defined in terms of another. Fourth, the presence of the direct interest rate component in the CPI tends to push optimal monetary policy in an expansionary direction. The net effect, considering also the traditional channel, however, depends on the nature of the initial disturbance. [source] Objective assessment of neurotoxicity while shifting from carbamazepine to oxcarbazepineACTA NEUROLOGICA SCANDINAVICA, Issue 5 2004B. Clemens Objectives , Objective assessment of non-overt neurotoxicity of carbamazepine (CBZ) vs oxcarbazepine (OXC) in patients with difficult-to-treat partial epilepsy, who were resistant to CBZ treatment and were converted from CBZ monotherapy to OXC monotherapy. Material and methods , Therapeutically equivalent doses (150 mg OXC for every 100 mg CBZ) were compared in 20 adult patients. Neurological investigation, conventional and spectral EEG analysis, brainstem auditory evoked responses (BAER) were carried out in both treatment conditions. EEG and BAER data of 20 age-matched healthy controls helped interpretation. Primary target variables (electrophysiological parameters) were evaluated blindly. Results , There were no significant differences between treatment conditions concerning the neurological condition, lack of clinically evident neurotoxicity, seizure frequency and EEG spike frequency. OXC treatment was characterized by less delta, theta, and alpha power, more beta power, and significantly greater mean alpha frequency (P = 0.03 and 0.05 for the left and right occipital leads, respectively), than CBZ treatment. Interpeak latencies were prolonged in the CBZ condition as compared with normals (P = 0.01) and OXC (P = 0.02). Conclusion , In this cohort of patients substitution of OXC for CBZ was associated with significant normalization of electrophysiological parameters, indicating decreasing neurotoxicity while shifting from CBZ to OXC monotherapy. [source] | |||||||||||||