ABSTRACT
Usability is the extent to which a product can be used by specific users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use. The Nielsen’s usability model has been popularly used for system usability evaluation. This thesis introduces a modification to Nielsen’s usability evaluation model which was used to evaluate the usability status of digital libraries in tertiary institutions in Lagos State. The digital libraries used were that of University of Lagos, Lagos State Polytechnic and Federal College of Education, Akoka. This modified model incorporates four traditional attributes (Efficiency, Effectiveness, Satisfaction, Learnability) and two additional attributes (Discoverability and Cognitive Load) introduced by the researcher; these two attributes were introduced because they have been proven to be user centered attributes which will help in getting the users’ personal experience while using the software (digital library) unlike the existing usability evaluation models which were majorly system centered.
The digital libraries will be assessed using modified heuristic think aloud method. The study employed purposive sampling technique to select the three tertiary institutions that was used for the evaluation while Yaro Yamani formula was used to calculate the users’ population sample size of (40) for each of the institution. Six task based questionnaires were used to carry out test in collecting data for the study; they include: (i) Discover ability test, (ii) Cognitive Load test (iii) Learn ability test (iv) Effectiveness test (v) Efficiency test and (vi) Satisfaction test. The mean of each of the usability attributes were used to evaluate the usability status of the digital libraries of the selected institutions. IBM SPSS statistics version 21 was used to calculate the mean.
The result of the usability test carried out established that the digital libraries of the tertiary institutions in Lagos state were usable. It also indicated that the users of the digital libraries were satisfied with the use of the digital libraries in the investigated institutions. For the three institutions, discoverability has a mean of 14.65, cognitive load has a mean of 14.81, learnability has a mean of 16.21, effectiveness has a mean of 16.89, efficiency has a mean of 16.56 and satisfaction has a mean of 16.27. Usability results of the evaluated libraries showed that the digital libraries are: Effective, Efficient, Satisfactory, helps users to learn and the discoverability and cognitive load of the students are fast.
In conclusion, this study has successfully modified the Nielsen’s usability evaluation model by adding Discoverability and Cognitive Load to its constructs and this study has also contributed to literature. The modified Nielsen usability evaluation model is recommended for use to evaluate usability of other digital libraries in other tertiary institutions in Nigeria and Abroad.
TABLE OF CONTENTS
Content Page
Title Page i
Certification ii
Dedication iii
Acknowledgments iv
Abstract v
List of Tables ix
List of Figures x
List of Appendices xi
Chapter One Introduction
1.1 Background to the Study 1
1.2 Statement of the Problem 3
1.3 Objective of the Study 4
1.4 Research Questions 4
1.5 Significance of the Study 4
1.6 Scope of the Study 4
1.7 Methodology 5
1.8 Operational Definition of Terms 5
1.9 Organisation of Subsequent Chapters 5
Chapter Two Review of Literature
2.0 Introduction 6
2.1 Definition of usability 6
2.1.1 Attributes of usability 6
2.1.2 Importance of usability 8
2.1.3 The role of usability in digital libraries 9
2.2 Usability Evaluation Models 10
2.2.1 Usability in ISO 9126 10
2.2.2 ISO/IEC 9126-1 11
2.2.3 Usability in ISO 9241 12
2.2.4 ISO 9241-11 13
2.2.5 Dix et al usability evaluation model 14
Content Page
2.2.6 Nielsen usability evaluation model 15
2.2.7 Eason usability evaluation model 16
2.2.8 Enhanced usability evaluation model 17
2.2.9 Normative usability evaluation model 17
2.2.10 Modified Nielsen’s usability evaluation model 18
2.3 Usability evaluation methods 18
2.3.1 Card Sorting 18
2.3.2 Open card sort 19
2.3.3 Closed card sort 19
2.3.4 Cognitive walkthrough 19
2.3.5 Focus group 20
2.3.6 Think aloud 21
2.3.7 Contextual Inquiry 21
2.3.8 Heuristic evaluation 22
2.3.9 Questionnaire 23
2.4 Digital library 24
2.4.1 Role of digital library in Education 25
2.4.2 Sources of digital library 26
2.5 Review of closely related work on usability evaluation 29
Chapter Three Methodology
3.0 Introduction 33
3.1 Research Design 33
3.2 Population 33
3.2.1 UNILAG digital library 33
3.2.2 FCE. (T) Akoka digital library 34
3.2.3 LASPOTECH digital library 35
3.3 Sample size and sampling technique 36
3.4 Usability model design/development 37
3.5 Method of data collection 39
3.5.1 Think Aloud 39
3.5.2 Heuristic evaluation 39
Content Page
3.5.3 Modified heuristic think aloud method 40
3.5.4 Modified heuristic think aloud evaluation 40
3.6 Evaluation Tool 40
3.7 Tasks in Usability Testing 41
Chapter Four DATA ANALYSIS, Results and Discussion of Findings
4.0 Introduction 42
4.1 Results of Usability Tests 42
Research Question One 42
4.1.1 Discoverability Test 42
4.1.2 Cognitive Load Test 43
4.1.3 Learnability Test 44
4.1.4 Effectiveness Test 45
4.1.5 Efficiency Test 46
4.1.6 Satisfaction Test 46
Research Question Two 47
Chapter Five Summary, Conclusion and Recommendations
5.1 Summary 49
5.1.1 Summary of Findings 49
5.2 Conclusion 50
5.3 Recommendations 50
References 51
