Search results for "linear regression"
showing 10 items of 375 documents
Study on the determination of trace rhenium (VII) by the adsorption differential pulse polarography
1989
The determination of trace rhenium (VII) by differential pulse polarography in the system of H2SO4-(NHsOH)2 · H2SO4-TeO2−4 is markedly improved by the addition of Nitron, which is adsorbed on the surface of mercury electrode. The limit of detection is down to 2 × 1010 M. The adsorptive peak potential is −0.80 V (vs. SCE). In the ranges of 5 × 1010—10−8, 1 × 10−5—10−7 and 1 × 10−7—10−6M, there are good linear relationships between the peak current increment and the concentration, of which the relative standard deviations are 9.5, 6.6, 1.8% respectively with the correlation coefficients of linear regression of 0.995–0.999. The results relating to this polarographic wave show that it is an ads…
Agreement among 3 optical imaging methods for the assessment of optic disc topography.
2005
Purpose To assess the agreement of disc topography measurements between the Heidelberg Retina Tomograph (HRT II), Retinal Thickness Analyzer (RTA), and Optical Coherence Tomograph (StratusOCT). Design Observational cross-sectional study. Participants Forty-two randomly chosen eyes of 42 subjects. Methods Each subject underwent HRT II, RTA, and StratusOCT examination. Two experienced examiners drew the contour lines for the HRT II and RTA. Bland and Altman plots were used to evaluate agreement for each topographic parameter among the instruments. The Spearman coefficient of rank correlation was evaluated for each topographic parameter. Main Outcome Measures Agreement in the measurement of op…
THE RELATIONSHIP BETWEEN DIFFUSE AND TOTAL SOLAR RADIATION IN COMPUTER SIMULATION OF SOLAR ENERGY SYSTEMS
1978
ABSTRACT The diffuse to total radiation correlation developed by Liu and Jordan [1] was tested for three Italian locations. An acceptable agreement was found between the regression lines in [1] and the ones found for two of the three locations. Using measured hourly values of total solar radiation on a horizontal surface, the corresponding hourly values of total solar radiation on an inclined surface at 45° facing south were computed with both the Liu and Jordan and the Loudon [6] method for estimating the diffuse radiation. Results show that approximately the same degree of accuracy in the prediction is achievable with both methods and that the difference between the measured total monthly…
Application of the Wood model to lactation curves of Comisana sheep
1997
Abstract Ninety-two ewes of the Comisana breed were used in a study to verify the forecasting capacity of the mathematical model proposed by Wood for fitting sheep data, and to evaluate the effect of the environmental factors affecting the parameters of the lactation curve. The Wood model underestimated the total lactation milk production with an error margin of 12.2 ± 7.8 kg of milk corresponding to 10.9 ± 6.6%. There was a strong influence of order of lambing × lambing season interaction on the lactation parameters. The curves for the winter lambing ewes demonstrated a higher peak production than autumn lambing ewes (1728.4 vs. 1082.6 g, P ≤ 0.05 for the second lambing ewes and 1772.8 vs.…
Coefficient shifts in geographical ecology: an empirical evaluation of spatial and non-spatial regression
2009
12 páginas, 4 figuras, 3 tablas.
Measuring the gender wage gap—a methodological note
2019
We propose to estimate the Blinder-Oaxaca decomposition by a single-equation model augmented with interactions between the group membership and other predictors. The relative importance of predicto...
The exchange rates – indicators for assessing the financial performance of the companies from Romania
2016
Abstract The research aims to determine the financial performance of the companies listed and traded on the Bucharest Stock Exchange from the manufacturing sector in Romania, compared with the performance recorded by the Bucharest Stock Exchange, based on the exchange rates. It was concluded that the financial performance of the companies included in the research, quantified on the basis of the exchange rates, decreased significantly with the arrival of the financial and economic crisis, currently, the companies being unable to reach the level of performance recorded before the crisis.
European Natural Gas Seasonal Effects on Futures Hedging
2015
Abstract This paper is the first to discuss the design of futures hedging strategies in European natural gas markets (NBP, TTF and Zeebrugge). A common feature of energy prices is that conditional mean and volatility are driven by seasonal trends due to weather, demand, and storage level seasonalities. This paper follows and extends the Ederington and Salas (2008) framework and considers seasonalities in mean and volatility when minimum variance hedge ratios are computed. Our results show that hedging effectiveness is much higher when the seasonal pattern in spot price changes is approximated with lagged values of the basis (futures price minus spot price). This fact remains true for short …
Linear and nonlinear interest rate sensitivity of Spanish banks
2011
Abstract Interest rate risk is one of the major financial risks faced by banks due to the very nature of the banking business. The most common approach in the literature has been to estimate the impact of interest rate risk on banks using a simple linear regression model. However, the relationship between interest rate changes and bank stock returns does not need to be exclusively linear. This article provides a comprehensive analysis of the interest rate exposure of the Spanish banking industry employing both parametric and non-parametric estimation methods. Its main contribution is to use, for the first time in the context of banks’ interest rate risk, a nonparametric regression technique…
Influence of energy drinks on enamel erosion : in vitro study using different assessment techniques
2021
Background Dental erosion has become a relevant public health problem in recent years and is related to the increase in the consumption of acidic beverages. Objective: The aim of the present study was to evaluate the erosive potential of energy drinks on dental enamel using an in vitro erosion model. Material and Methods Thirty-eight blocks of human enamel were divided into four groups: G1- TNT Energy Drink®(n=8), G2- Red Bull® (n=10), G3- Monster Energy® (n=10), and G4- Coca-Cola® (n=10) (positive control). For the chemical analysis, the pH values, titratable acidity, and buffering capacity of the beverages were measured in triplicate. For the erosive test, the specimens were immersed in t…