The progress in information and communication technologies and the birth of the internet has changed the end user computing experience and environment. This advancement has changed the way of delivering information and services. Information systems can now be web-enabled, unlike the traditional stationary information systems. Web portals are a part of this advancement. A Web portal is a gateway to information and services from multiple sources in a unified way, using a single, unique user interface (Tatnall, 2005). A Web portal usually features specific functions, such as search mechanisms, access to databases, user registration and personalization options. The use of web portals offered universities and postgraduate education huge opportunities for expansion, introduction of new services and development of both qualitative and quantitative ways of delivering information and services. More also, the need to satisfy the information requirements of postgraduate students in the University of Ibadan has brought about the large scale investment in the Postgraduate School web portal. There is therefore need on the part of the stakeholders to justify the huge investment in this area by measuring the impact of the information system on end-user satisfaction. The end-user satisfaction is regarded as the individual's attitude toward computer uses, or related activities required to perform tasks in an organization (Rainer and Harrison, 1993).
Aim of the Study
The major aim of this study was to investigate how information system IS measures such as system quality, information quality, service quality, technological/infrastructural issues, users' IT self-efficacy influence user satisfaction of the university of Ibadan postgraduate school web portal.
The primary data were collected through the administered questionnaires, responses were collected, and the results were analysed.
The research design adopted for this study is survey. It involves the systematic collection of information from the postgraduate school portal users who are postgraduate students. Their opinions are expected to provide an understanding of the assessment of the user satisfaction level of the portal system.
Sample and sampling techniques
This study used proportional stratified sampling technique to select a sample size of 385 postgraduate students. This represents 5% of the population (7,688). This number is considered sufficient due to time and cost factors. Proportional stratified sampling strategy is chosen for this study since each faculty represent a stratum and proportionality is applied so that the same percentage of elements from each stratum is drawn. Simple random sampling was used to select the respondents from each stratum. This probabilistic approach ensures that every element in the population has equal chance of being included in the study.
A self-structured questionnaire built from the constructs of DeLone and McLean (2003) model was used to collect the primary data from the respondents of the study. The questionnaire was sectioned into five parts.
Section A: This section collects demographic information of the respondents.
Section B: This section contained questions on the user's perception of system quality of PG school web portal.
Section C: This section contained questions on the user's perception of information quality of PG school web portal.
Section D: This section contained questions on the user's perception of service quality of PG school web portal.
Section E: This section contained questions on the user's perception on technology and infrastructure issue affecting the PG school web portal.
Section F: This section contained questions on the user's I.T self-efficacy.
Section G: This section contained questions on the user's satisfaction affecting the PG school web portal.
Validity of instrument
The questionnaire used for this study was designed based on the study's conceptual model by the researcher. Subsequently the questionnaire was critically reviewed to ensure its face and content validity.
Reliability of Instrument
The variables for each of the construct used in the study instrument were subjected to a reliability test using the Cronbach alpha scale, the resulting Cronbach alpha coefficient values were higher than the 0.6 threshold with the overall user satisfaction construct been the highest, this further ascertain the reliability of the measuring instrument.
Method of data collection
The questionnaires were distributed to the sample size of the postgraduate students in every faculty of the University of Ibadan. The researcher and two of her assistants helped in the administration of the questionnaires.
PRESENTATION OF RESULTS AND DISCUSSION
The ever increasing budget on information technology (IT) by organizations even in the face of potential economic downturns are well documented in literature Kanaracus, (2008), despite pressures to cut costs. This has necessitated the need for organizations to measure and examine the benefits and costs of technology. According to Petter et al., (2008), the impacts of IT are often indirect and influenced by human, organizational, and environmental factors; therefore, measurement of information systems (IS) success is both complex and illusive. There are IS that range from hedonic, developed for pleasure and enjoyment, to utilitarian, developed to improve individual and organizational performance Van der Heijden, (2004). Organizations focus on developing, using, and evaluating utilitarian IS.
There is an excess of utilitarian IS used in organizations, such as decision support systems, computer-mediated communications or web portal system, e-commerce, knowledge management systems, as well as many others. However, this study considered the web portal utilitarian information system and how users (postgraduate students) perceive its functionality in satisfying their demands on the system. The results in the proceeding tables show the wholesome significance of the information system dimensions on user satisfaction and how IT self-efficacy mediates such relationships. The discussion is based on the outcomes of...