Gabriel Okyere - Academia.edu (original) (raw)

Papers by Gabriel Okyere

Business Strategy & Development

International Journal of Mathematics Trends and Technology

As a sequel to previous papers, we assess, in a more general form, the performance of real income... more As a sequel to previous papers, we assess, in a more general form, the performance of real income per head / capita using generalized aggregate production function under optimal control conditions. The role of the population growth dynamics in all of this is carefully tracked, especially as it varies from primarily exponential to sturdily logistic. Analytical, qualitative and numerical simulation procedures are used to decode the population associated parameters that engender qualitative variations in the evolution of real income per head. Non-labour factors of production per effective labour are here used as the state vector, whereas the output variable is income per effective labour, whilst consumption and investments relative to the above production factors, per effective labour apiece, become the control vector. The quadratic cost functional consisting of the control and state vectors, time-discounted, turns the objective functional. Largely, real income per head rises much quic...

Heliyon, 2019

This article evaluates the accuracy of effect-size estimates for some estimation procedures in me... more This article evaluates the accuracy of effect-size estimates for some estimation procedures in meta-analysis. The dilemma of which effect-size estimate is suitable is still a problem in meta-analysis. Monte Carlo simulations were used to generate random variables from a normal distribution or contaminated normal distribution for primary studies. The primary studies were hypothesised to have equal variance under different population effect sizes. The primary studies were also hypothesised to have unequal variance. Meta-analysis was done on the simulated hypothesized-primary-studies. The effect sizes for the simulated design of the primary studies were estimated using Cohen's , Hedges' , Glass' △, Cliff's delta and the Probability of Superiority. Their corresponding standard error and confidence interval were computed and a comparison of an efficient estimator was done using statistical bias, percentage error and confidence interval width. The statistical bias, percentage error and confidence interval width pointed to Probability of Superiority as an accurate effect size estimate under contaminated normal distribution, and Hedges' as the most accurate effect size estimates compared to Cohen's and Glass' △ when equal variance assumptions are violated. This study suggests that the accuracy of effect size estimates depends on the details of the primary studies included in the metaanalysis.

The possible dominance of basic assumption about underlying models on the analysis of data is of ... more The possible dominance of basic assumption about underlying models on the analysis of data is of much concern. This study aimed develop a robust fitting procedure for one-way ANOVA models under adaption on the observed samples. Further investigation on Asymptotic Relative Efficiency (ARE) of this procedure and parametric F-test under class of continuous distributions was performed. 10,000 simulations were carried out for a one-way ANOVA model with three levels for sample sizes 5, 10, 15, and 20. Intralevel correlation coefficient 0 ρ = was considered in the these simulations. The findings revealed that the parametric F-test for oneway ANOVA model performed better than the non-parametric Adaptive test proposed for symmetric and moderate tailed distributions and then in symmetric and light tailed distributions with ARE between 2% and 55%. However, the Adaptive test outperformed the F-test in symmetric and asymmetric with varying tail weights distributions with ARE between 4% and 64%. ...

International Journal of Sciences Basic and Applied Research, May 24, 2014

Cluster comorbidity explains statistically significant associations between diseases without etio... more Cluster comorbidity explains statistically significant associations between diseases without etiological explanation. Our prior study shown that multimorbidity can be separated into three clinically consistent clusters, namely gastrointestinal low back pain and anxiety disorders (GLAD), cardio-metabolic and pain disorders (CMPD), and cardio-pulmonary disorders (CPD). The aim of this study is to assess the extent at which each cluster influences the survival of elderly patients. The study utilized follow-up clinical data of 154 inpatients in the age group 50+ from a health facility in Ghana. The dataset was computationally formatted as right censored from which the Gompertz survival model was fitted. Overall, 61 mortalities were observed, of which 52.5%, 32.7% and 14.8% were patients with diseases classified under CMPD, CPD and GLAD respectively. We demonstrated that the pattern of survivorship of these patients is Gompertz distributed. As per our model, we found that the risk for mortality associated with the comorbidity clusters increases exponentially over the length of hospital stay. The patients with diseases classified under CPD and CMPD have increased risk for mortality with hazard ratio (HR) of 3.85 and 3.76 respectively, compared to GLAD with HR of 1.0.

Universal Journal of Public Health, 2015

In most epidemiological data sets one cannot be certain that all risk factors are measured or obs... more In most epidemiological data sets one cannot be certain that all risk factors are measured or observed. This paper studies the risk for mortality associated with diseases and deals with heterogeneity in mortality owing to unobserved covariates. We extracted medical records of 186 hospitalized patients from an urban health facility in Ghana. Patients with at least 2 diagnoses of chronic diseases were considered multimorbid. Using age of patients at death as survival time we executed our analysis with and without incorporating frailty effect to Cox proportional hazards (PH) model. The Cox PH model with Gaussian frailty fitted the data better when compared to the standard Cox PH model and Cox PH model with gamma frailty. On average patients were aged 62.3±15.3 years, with 66.1% being multimorbid. Varying degrees of mortality risks were found for different diseases, with the highest associated with having pulmonary valve disorders (HR 7.99, 95% CI 1.45-44.0). Heterogeneity in mortality resulting from unmeasured factors was insignificant. This study demonstrates that patients share similar risk with respect to unobserved factors, but varying risk when conditioned on observables.

International Journal of Scientific and Engineering Research

This paper seek to predict new HIV cases in the Ashanti region of Ghana using Holt's exponent... more This paper seek to predict new HIV cases in the Ashanti region of Ghana using Holt's exponential smoothing and the Box-Jenkins ARIMA model of time series analysis. The Holts exponential smoothing predicted 2580 new HIV cases per year in Ashanti region whereas the Box-Jenkins ARIMA model predicted a constant number of 2556 new HIV cases per year, suggesting that the epidemic in the Ashanti region will relatively be in stable equilibrium for the next three years. Keywords—Box-Jenkins ARIMA model, HIV in Ashanti region, Holt's exponential smoothing, Time series forecast.

International Journal of Academic Research in Economics and Management Sciences, 2014

In this paper, we investigate the linkage between FDI and economic growth using macro econometric... more In this paper, we investigate the linkage between FDI and economic growth using macro econometric model in the Ghanaian context. Structural shocks in an SVAR model were used to identify the contemporaneous and short run relationships effects of these variables. The AB model restriction approach was used for the Identification and was compared to the Cholesky decomposition. We showed that, there exit a contemporaneous short run positive effects of FDI inflows on GDP growth but as the time horizon expands these effects tend to converge to the equilibrium, however FDI's deteriorate domestic investment.

International journal of statistics and applied mathematics, 2021

This paper seeks to find a Robust Adaptive Scheme for models with dependent error structure. The ... more This paper seeks to find a Robust Adaptive Scheme for models with dependent error structure. The design considered for the paper is Repeated Measures Design. The defining characteristics of repeated measures data are the dependency and covariance structure. The objectives of repeated measures data analysis are to examine and compare response trends over time. The nine winsorised scores proposed by Hettmansperger are used because they are considered the most appropriate set of rank scores for hypothesis testing and accommodate a broad class of continuous distributions which are either symmetric or asymmetric with varying tailweights. The Adaptive Scheme which this paper seeks to find for models with dependent error structure is a two-step procedure in which a selector statistic is first used to examine and classify a given data based on measures of skewness and tailweight. Afterwards, a test statistic, independent of the selector statistic is chosen and a test conducted. A simulation study was conducted to compare the performance of the adaptive test and the traditional parametric test from different continuous distributions. Analysis of real data sets were as well performed to compare efficiency of the two tests. The findings favoured the adaptive test especially for data generated from nonnormal distributions. Our adaptive scheme proved robust and efficient over the parametric test when a data contains outliers. The paper considered four covariance structures namely; Compound Symmetry (CS), Unstructured (UN), First Order Autoregressive (AR (1)) and Autoregressive with Heterogeneous Variance (AHR (1)). On the basis of the values of Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC), the best covariance structure is selected.

Academic success in further mathematics is perceived to have a significant contribution towards t... more Academic success in further mathematics is perceived to have a significant contribution towards the development of science and technology in any nation. The main objective of this study is to identify the major determinants of students' academic success at WASSCE further mathematics. Two public schools in Hemang Lower Denkyira District constituted the study area with a sample of 84 students. Data for 2016/1017 WASSCE academic year group tracked from the documented records of the two selected schools in the District with 1:1 gender ratio were used for the study. Explanatory factors were; Mock examination, Age, Student Residence, School Location, and Gender on the target variable WASSCE grade. A three-stage stratified cluster sampling technique was used to select the two schools as well as classes and subject area under study. IBM SPSS Version 21 was used to analyse the data for the purpose to modelling multiple logistic regression with a binary response 'WASSCE grade' (up...

An article by Tawiah, Richard; Bruce Lamptey, Richard; Okyere, Gabriel Asare; Oduro, William; and... more An article by Tawiah, Richard; Bruce Lamptey, Richard; Okyere, Gabriel Asare; Oduro, William; and Thompson, Michael Oko, "Review of ELearning Environment at the Kwame Nkrumah University of Science and Technology, Ghana" (2019). Library Philosophy and Practice (e-journal). 2337; https://digitalcommons.unl.edu/libphilprac/2337

This paper seeks to build a deterministic optimal control model to fit the Ghanaian economy. The ... more This paper seeks to build a deterministic optimal control model to fit the Ghanaian economy. The model looks at a simple closed economy with government participation. The Hamilton-Pontryagin’s theory was employed to analyze the systems obtained. Numerical simulations were also used to obtain numerical solutions to the model. Results obtained from the analysis performed suggest that the system is controllable. The short to long term predictions of the system are generally very good. The results obtained also suggest that the 2020 goal of Ghana becoming a middle income economy is attainable if the control measures prescribed are applied.

This paper focuses on the qualitative dynamics of the Ramsey-Cass-Koopmans (RCK) growth model wit... more This paper focuses on the qualitative dynamics of the Ramsey-Cass-Koopmans (RCK) growth model with exponential growth of labour (population) and RCK with logistic growth rate of labour. We find parameter values at which qualitative changes occur. A continuation method was employed in analyzing the qualitative behavior of the various models at the equilibrium state under the variation of a single parameter. We detected a co-dimension one hopf point (H) denoting a sub-critical hopf bifurcation, neutral saddle hopf point (H) and a branch point (BP) in these models. The bifurcation points for discount rate parameter and the coefficient of relative risk aversion parameter were not economically substantive.

The field of microfinance in Ghana has observed a steady growth in recent years, especially the l... more The field of microfinance in Ghana has observed a steady growth in recent years, especially the last decade has seen an accelerated growth in the field of microfinance in terms of activities and infrastructure by both the government and nongovernmental organizations in rural areas where hitherto in some years ago would have been a no go areas. Microfinance has been considered as an important tool to development in the Sub-Saharan Africa and third world countries in general. It has also been seen as tool for enhancing the general wellbeing of the people living in this category of countries. The term microfinance in practise relates to the lending of very small loans to poor people in order to establish a means of alleviating poverty by given the poor an opening to begin a business or to improve an existing Abstract: The aim of this study is to examine the influence of social networks on the utilization of business development programs and the experience of improvement in businesses o...

This research was done within the framework of intervention time series analysis to assess the na... more This research was done within the framework of intervention time series analysis to assess the nature and impact of the establishment and operations of community policing in communities in Ghana. In line with this objective, a secondary data made up of monthly serious crimes from 2000 to 2011 were obtained from Regional Criminal Investigations Department (CID), Eastern Regional Command of Ghana Police Service.An autoregressive integrated moving average, (ARIMA (1,1,0)) models were constructed to analyse the pre and post intervention of serious crimes respectively. Based on the ARIMA(1,1,0) model for the pre-intervention series, a full intervention model was obtained.The intervention strategy was found to have reduced serious crime by 16 cases per month. The reduction was abrupt but temporal and statistically significant at 5% level. However, the statistically insignificant rate of decay () of 0.0369 at 5% level resulted in the temporal effect of the intervention. The overall interve...