Effect of Multicolinearity and Autocorrelation on Predictive Ability of Some Estimators of Linear Regression Model

Violation of the assumptions of independent regressors and error terms in linear regression model has respectively resulted into the problems of multicollinearity and autocorrelation. Each of these problems separately has significant effect on parameters estimation of the model parameters and hence prediction.  This paper therefore attempts to investigate the joint effect of the existence of multicollinerity and autocorrlation on Ordinary Least Square (OLS) estimator, Cochrane-Orcutt (COR) estimator, Maximum Likelihood (ML) estimator and the estimators based on Principal Component (PC) analysis on prediction of linear regression model through Monte Carlo studies using the adjusted coefficient of determination goodness of fit statistic of each estimator. With correlated normal variables as regressors, it further identifies the best estimator for prediction at various levels of sample sizes (n), multicollinearity  and autocorrlation . Results reveal the pattern of performances of COR and ML at each level of multicollinearity over the levels of autocorrelation to be generally and evidently convex especially when  and while that of OLS and PC is generally concave. Moreover, the COR and ML estimators perform equivalently and better; and their performances become much better as multicollinearity increases. The COR estimator is generally the best estimator for prediction except at high level of multicollinearity and low levels of autocorrelation. At these instances, the PC estimator is either best or competes with the COR estimator. Moreover, when the sample size is small (n=10) and multicollinearity level is not high, the OLS estimator is best at low level of autocorrelation whereas the ML is best at moderate levels of autocorrelation. .Keywords: Prediction, Estimators, Linear Regression Model, Multicollinearity, Autocorrelation

G´en´etique Clinique dans le Service de P´ediatrie et de G´en´etique M´edicale du Centre National Hospitalier et Universitaire de Cotonou : Etat des Lieux et Perspectives

Il s’agissait d’une ´etude r´etrospective descriptive portant sur les patients rec¸us en consultation de g´en´etique m´edicale de Septembre 2004 `a Aoˆut 2007. Les patients b´en´eficiaient des examens dysmorphologique et physique, des bilans cytog´en´etiques et/ou mol´eculaires, des interventions th´erapeutiques et un suivi `a long terme. Les variables ´etudi´ees ´etaient les donn´ees sociod´emographiques et cliniques. Soixante et seize patients ont ´et´e rec¸us durant la p´eriode avec une pr´edominance masculine (57,89%). Les motifs de consultation ´etaient domin´es par le retard psychomoteur (38,15%), la dysmorphie faciale (30,26%) et les malformations (19,73%). Les principales malformations portaient sur les extr´emit´es et la face. Les pathologies confirm´ees comprenaient des aberrations chromosomiques (46,05%) avec une pr´edominance de la trisomie 21 et des maladies monog´eniques (7,89%). Le rendement de nos recherches pourrait ˆetre am´elior´e par l’acc`es `a la technique FISH. C’est une exp´erience quasi unique en Afrique de l’ouest et permet d’apporter des r´eponses aux personnes souffrant d’affections h´er´editaires.Mots Cl´es g´en´etique clinique ; retard psychomoteur ; dysmorphie ; malformation ; aberration chromosomique ; maladie monog´eniqu

Macroeconomic Shocks and Employment in sub-Sharan Africa: Do Labour Market Institutions Matter?

The effects of macroeconomic shocks and labour market institutions on employment in sub-Saharan African countries are examined in this study. Using a sample of 27 SSA countries for the period 2007 to 2018, both linear and interactive relationships are investigated. The results show that labour market institutions (especially in terms of wage flexibility) dampen the effects of shocks on modern employment but amplify the effects of shocks on informal employment in the sampled SSA countries. There is also evidence that shocks themselves (especially those emanating from the external sector) do not matter for a huge proportion of employment changes in SSA countries. Rather, the direct effects of shocks on employment are more profound in the formal sector. The study therefore concludes that reforming the informal sector will help to ensure the effectiveness of labour market institutions in mitigating the negative impacts of external shocks on employment in SSA

The Challenges and Panaceas to Power Distribution Losses in Nigeria

Energy losses in the distribution network and its subsystems have been issues of great concerns in Nigeria’s power sector. For decades, several studies have been conducted on the challenges facing the power sector in Nigeria with most focus directed on the distribution subsystems. The major challenge in the distribution system is the high energy losses which are detrimental to the techno-economic benefits of the power systems. However, details of the distribution system challenges and the probable solutions have not been efficiently presented. In this study, some of these challenges are presented and the potential solutions are proposed. The features of the Nigeria distribution network, the technical and non-technical sources of losses as well as the identified challenges are presented before discussing the potential solutions. The panaceas so provided were from the understanding of some published works and other related materials as well as the in-depth understanding of the authors. This article can serve as a guide for the utilities and stakeholders in the power sector for efficient management operations and improved customer service delivery

The Influence of Annealing Temperatures on the Ductility and Toughness of Springs

ABSTRACT This study was carried out to investigate the influence of annealing temperatures on the ductility and impact toughness of springs. The springs were made from mild steel rod having a diameter of 6mm. The springs were then subjected to annealing process at temperatures of 650 o C, 700 o C, and 850 o C. The annealed springs were tested for ductility and impact toughness. The annealed spring became softer with increase in the annealing temperature; its percentage elongation, or ductility, increased from 18.75% to 30% and later 42.5 % with increase in annealing temperature. The impact toughness increased from 40 J to 45J and later to 49 J. The Rockwell hardness values however reduced from 30 RC to 23 RC and later 20 RC as annealing temperature increased

The effect of pyridoxine supplementation on quality of life of patients with chronic lymphocytic leukaemia

Objective: Pyridoxine, is essential in the metabolism of many classes of food, we aimed at determining the effect of its supplementation on the quality of life (QoL) of patients with chronic lymphocytic leukaemia (CLL).Methods: This study compared the (QoL) and haematological parameters of CLL patients before and after the administration of pyridoxine. Data obtained were analyzed using SPSS version 19.Results: There was improvement in the QoL of the patients after pyridoxine supplementation; Majority of the parameters that make up the physical functional scales was significantly higher after pyridoxine supplementation. There were also significant improvements in insomnia, appetite loss and constipation after pyridoxine supplementation.Conclusion: Pyridoxine supplementation in patients with CLL marginally improved quality of life.Keywords: Pyridoxine, Supplementation, Quality of life, Leukaemia, CL

ATR-mediated phosphorylation of DNA polymerase η is needed for efficient recovery from UV damage

DNA polymerase η (polη) belongs to the Y-family of DNA polymerases and facilitates translesion synthesis past UV damage. We show that, after UV irradiation, polη becomes phosphorylated at Ser601 by the ataxia-telangiectasia mutated and Rad3-related (ATR) kinase. DNA damage–induced phosphorylation of polη depends on its physical interaction with Rad18 but is independent of PCNA monoubiquitination. It requires the ubiquitin-binding domain of polη but not its PCNA-interacting motif. ATR-dependent phosphorylation of polη is necessary to restore normal survival and postreplication repair after ultraviolet irradiation in xeroderma pigmentosum variant fibroblasts, and is involved in the checkpoint response to UV damage. Taken together, our results provide evidence for a link between DNA damage–induced checkpoint activation and translesion synthesis in mammalian cells