Ezekiel N. N. Nortey

Determinants of Automobile Purchase and Brand Choice in Ghana: Multinomial Logit Approach

This study expands on previous studies by examining the purchasers’ criteria choice of automobile in the Ghanaian market and establishing the factors that influence the purchase and estimating the choice of brand. The study examined 1,130 automobile owners. Data was collected on 20 automobile attributes considered important when purchasing an automobile. The preliminary result of the research show that five major factors— interior, safety, value for money, modernity, and economy—influence consumers to purchase a particular automobile. Conclusion can be drawn that a relationship exists between the influencing factors and the brands of automobiles purchased by respondents.

Possible adverse effect of high delta-alpha-tocopherol intake on hepatic iron overload: enhanced production of vitamin C and the genotoxin, 8-hydroxy-2'- deoxyguanosine.

Excess hepatic iron generates reactive oxygen species that result in oxidative stress and oxidative damage to the liver. Vitamins have hitherto been considered to be a possible remedy. The aim of this study was to determine if high doses of δ-α-tocopherol supplementation in iron overload would ameliorate the oxidative stress. Four groups of 20 male Wistar albino rats were studied: group 1 (control) was fed normal diet, group 2 (Fe) 0.75% Ferrocene iron, group 3 (FV gp) 0.75% Ferrocene/δ-α-tocopherol (10× RDA), group 4 (V gp) normal diet/δ-α-tocopherol. After 12 months, serum iron, reduced glutathione, catalase, vitamin C, Oxygen Radical Absorbance Capacity, lipid peroxidation, 8-hydroxy-2′-deoxyguanosine (8-OHdG), aspartate transaminase (AST), and alanine transaminase (ALT) were measured. Vitamin C levels were: F gp = 5.04 ± 0.09; FV gp = 5.85 ± 0.13 (μmol/l) (p < 0.05). 8-hydroxy-2′-deoxyguanosine levels were: F gp = 143.6 ± 6.4; FV gp = 179.2 ± 18.2 (ng/ml) (p < 0.05). Oxidative liver damage, as determined by serum AST and ALT levels, was not attenuated by α-tocopherol. A positive correlation existed between vitamin C and 8-OHdG, suggesting possible δ-α-tocopherol toxicity.

A Study of the Estimation of the Gini Coefficient of Income Using Lorenz Curve

DOI: 10.9734/BJMCS/2016/24494 Editor(s): (1) Sun-Yuan Hsieh, Department of Computer Science and Information Engineering, National Cheng Kung University, Taiwan. Reviewers: (1) Johan Fellman, Swedish School of Economics and Business Administration, Finland. (2) Todd Christopher Headrick, Southern Illinois University Carbondale, USA. Complete Peer review History: http://sciencedomain.org/review-history/13807

A Proposed Numerical Integration Method Using Polynomial Interpolation

The main aim of this paper is to propose a numerical in tegration method using polynomial interpolation that provides improved estimates as compared to the Newton-Cotes methods of integration. The method is an extension of trapezoidal rule where the Lagrange inter polation is employed when fitting polynomials after segmentation. We proved that the proposed numerical integrat ion method using polynomial interpolation provided an improved formula for numerical integra tion. The proposed method using polynomial interpolation gave better estimates as compare d to some Newton-Cotes methods of integration.

A Simulation Comparison of Estimators of Conditional Extreme Value Index under Right Random Censoring

In extreme value analysis, the extreme value index plays a vital role as it determines the tail heaviness of the underlying distribution and is the primary parameter required for the estimation of other extreme events. In this paper, we review the estimation of the extreme value index when observations are subject to right random censoring and the presence of covariate information. In addition, we propose some estimators of the extreme value index, including a maximum likelihood estimator from a perturbed Pareto distribution. The existing estimators and the proposed ones are compared through a simulation study under identical conditions. The results show that the performance of the estimators depend on the percentage of censoring, the underlying distribution, the size of extreme value index and the number of top order statistics. Overall, we found the proposed estimator from the perturbed Pareto distribution to be robust to censoring, size of the extreme value index and the number of top order statistics.

Erratum to: Estimation of the Gini coefficient for the lognormal distribution of income using the Lorenz curve

[This corrects the article DOI: 10.1186/s40064-016-2868-z.].

Extreme value modelling of Ghana stock exchange index

AbstractModelling of extreme events has always been of interest in fields such as hydrology and meteorology. However, after the recent global financial crises, appropriate models for modelling of such rare events leading to these crises have become quite essential in the finance and risk management fields. This paper models the extreme values of the Ghana stock exchange all-shares index (2000–2010) by applying the extreme value theory (EVT) to fit a model to the tails of the daily stock returns data. A conditional approach of the EVT was preferred and hence an ARMA-GARCH model was fitted to the data to correct for the effects of autocorrelation and conditional heteroscedastic terms present in the returns series, before the EVT method was applied. The Peak Over Threshold approach of the EVT, which fits a Generalized Pareto Distribution (GPD) model to excesses above a certain selected threshold, was employed. Maximum likelihood estimates of the model parameters were obtained and the model’s goodness of fit was assessed graphically using Q–Q, P–P and density plots. The findings indicate that the GPD provides an adequate fit to the data of excesses. The size of the extreme daily Ghanaian stock market movements were then computed using the value at risk and expected shortfall risk measures at some high quantiles, based on the fitted GPD model.