Using Item Response Theory to Understand Item-Nonresponse (Missing Data) in Ghanaian Surveys
After reviewing the theoretical and empirical literature on Item Response Theory (IRT) and Item-non response, this study investigates three issues: Firstly, to identify the most appropriate IRT model for understanding item-non response...
World cocoa production, processing and chocolate consumption pattern
Achieving optimal investment portfolio using dynamic programming
Ben Apau-Dadson, Iddrisu Wahab Abdul, Joseph Dadzie, Martin Owusu Amoamah
Research Journal of Finance and Accounting
Cocoa cultivation, bean composition and chocolate flavour precursor formation
An Item Response Model for Understanding Item Non-response in Ghanaian Surveys
Survey research has been widely used in public opinion research in Ghana. Ghanaian researchers are happy about data richness and they are also concerned about data quality. In this paper Item Response Theory (IRT) has been used to identify the most appropriate IRT model for understanding item. The techniques are appropriate and practical. A questionnaire data on Ghana collected in the 5th wave of the World Values Survey was used for the analysis. The five categories of survey questions that are most difficult to answer by respondents were Life Related Questions, Value Related Questions, Political Related Questions, Income Related Questions and Democracy Related Questions. Missing or ‘don’t know’responses were assigned a 0 score, and 1 was assigned to answered items. The data was analysed based on four IRT models namely, the constrained Rasch model, the unconstrained Rasch model, the two parameter logistic model, and the three parameter logistic model. These models were explored to determine the most appropriate model for the data. In this paper, the unconstrained Rasch model emerged as the best model for understanding item non-response. We found that, income related questions had the highest difficulty parameter, hence the most difficult category of survey questions to answer. It was also found that, if an individual does not answer a survey question or give a ‘don’t know’answer, it is not only because of the question’s difficulty but also because the respondent doesn’t want to answer.
Effect of spontaneous fermentation and amylase-rich flour on the nutritive value, functional and viscoelastic properties of cowpea-fortified nixtamalized maize
Studies were conducted to evaluate the combined effects of spontaneous fermentation and amylase-rich flours (ARF) on some nutritive value, functional and viscoelastic properties of cowpea-fortified nixtamalized maize. A 2 × 3 × 3 factorial design, with fermentation medium, fermentation time and ARF level, was performed. The blends were fermented for the specific times and analysed for their titratable acidity, pH, water absorption capacity, viscoelastic properties, texture, protein and mineral content. Fermentation and ARF addition influenced titratable acidity, pH, water absorption, viscoelastic properties and texture of the cowpea-fortified nixtamalized maize. Addition of ARF decreased the viscoelastic properties, texture and pH of all the blends with a corresponding increase in acidity. Slight increases in protein and ash contents were noted with products fermented in coconut water, but ARF addition had only a …
Emmanuel Ohene Afoakwa, Philip Roger Aidoo, Randy Adjonu
Application of Macrobenthic Faunal Indices in Assesssing the Ecological Quality Status of Laloi Lagoon of Ghana
The aim of this study was to assess the macrobenthic fauna structure and use its indices as a tool for characterizing the ecological state of the Laloi lagoon. Thus, a field assessment of the benthos in the Laloi lagoon was carried in January 2012. Four replicate samples were taken at each station contained in three zones and analysed for their structure and composition. Twenty-one (21) species of macrobenthos belonging to 19 genera were identified. The highest number of species belonged to Polychaetes (15 species) followed by Bivalves (6 species) and 1 species of Gastropod. The grain size of sediments and total organic matter as essential factors in distribution and population diversity of macrobenthos communities were also analysed. The results showed that all of the stations were characterized by medium sand to very fine sand. Shannon-Wiener index (H'), species richness (S) and Pielou’s evenness were calculated and they revealed a high species diversity with variability in abundance within stations. The ecological indices, such as (AMBI, M-AMBI, BENTIX and H’) were also applied to the available benthic species data to determine the ecological status of the lagoon. AMBI, M-AMBI, H'and BENTIX gave different results regarding the boundaries for High, Good and Moderate and it was worse when applying H'and BENTIX. However, the index AMBI provided a more suitable evaluation of EcoQS corresponding to ‘slightly polluted’lagoons in compliance with univariate community indices.
Rita Esi Ampiaw, Martin Owusu Amoamah, Iddrisu Wahab Abdul, Joseph Dadzie
Optimum crop production and income in Brong Ahafo Region.
This paper seeks to present a proposed linear programming model to determine the best hectare allocation for optimum crop production to ensure food security and reduce poverty among farmers in the region. Five selected crops in fifteen sampled communities in the Brong Ahafo Region were used for this study. The net income per hectare for each crop was used in formulating the objective function and data on available arable land, mean annual rainfall and the area cultivated constitutes the constraints. The revised simplex scheme was employed to determine optimal basic variables.
Kwaku Fordark Darkwa, Kyegabador K Amos, Iddrisu Wahab Abdul
Microstructural and physicofunctional characterization of starches from selected cowpea (Vigna unguiculata L. Walp) varieties developed for pest and disease resistance
The microstructure, physico-chemical and functional properties of legume starches affect their cooking quality as well as the texture and rheological behaviour of foods processed from them. Thus, this study sought to establish the microstructural, physico-chemical and functional properties of the native starches of four cowpea varieties-Bengpla, Asetenapa, Asontem and CR-06-07, that have been developed against disease and pest infestation. The starches were extracted from the cowpeas and their gelation capacity, pasting characteristics, solubility, swelling volume and swelling power were studied using standard analytical methods. Microstructures of the starches were examined using light microscopy. Isolated starch granules from the microstructural examination showed irregular shapes with predominance of spheroid and oval forms in varying sizes. Starch granule sizes ranged from 1.9 mm in Asetenapa to 2.9 mm in Asontem. Swelling power, solubility and swelling volume at 95 C was highest in Bengpla with Asetenapa recording the lowest. However Asontem had the highest value in terms of solubility. With the exception of gelation capacity, significant differences (P≤ 0.05) were observed in all the studied parameters amongst the different cowpea varieties. Thus, the cowpea starches showed wide variations in microstructure, physico-chemical and functional properties among the studied varieties and these could be used in the selection of the varieties for specific food processing applications.
C Atuobi, E Sakyi-Dawson, S Sefa-Dedeh, EO Afoakwa, AS Budu
Research Article Modelling Trends of Climatic Variability and Malaria in Ghana Using Vector Autoregression
Malaria is considered endemic in over hundred countries across the globe. Many cases of malaria and deaths due to malaria occur in Sub-Saharan Africa. The disease is of great public health concern since it affects people of all age groups more especially pregnant women and children because of their vulnerability. This study sought to use vector autoregression (VAR) models to model the impact of climatic variability on malaria. Monthly climatic data (rainfall, maximum temperature, and relative humidity) from 2010 to 2015 were obtained from the Ghana Meteorological Agency while data on malaria for the same period were obtained from the Ghana Health Service. Results of the Granger and instantaneous causality tests led to a conclusion that malaria is influenced by all three climatic variables. The impulse response analyses indicated that the highest positive effect of maximum temperature, relative humidity, and rainfall on malaria is observed in the months of September, March, and October, respectively. The decomposition of forecast variance indicates varying degree of malaria dependence on the climatic variables, with as high as 12.65% of the variability in the trend of malaria which has been explained by past innovations in maximum temperature alone. This is quite significant and therefore, policy-makers should not ignore temperature when formulating policies to address malaria.
Sylvia Ankamah, Kaku S Nokoe, Wahab A Iddrisu