Browsing by Author "Kim, Sunha"

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    A Comparison of Discrete and Continuous Survival Analysis
    Kim, Sunha (Virginia Tech, 2014-05-08)
    There has been confusion in choosing a proper survival model between two popular survival models of discrete and continuous survival analysis. This study aimed to provide empirical outcomes of two survival models in educational contexts and suggest a guideline for researchers who should adopt a suitable survival model. For the model specification, the study paid attention to three factors of time metrics, censoring proportions, and sample sizes. To arrive at comprehensive understanding of the three factors, the study investigated the separate and combined effect of these factors. Furthermore, to understand the interaction mechanism of those factors, this study examined the role of the factors to determine hazard rates which have been known to cause the discrepancies between discrete and continuous survival models. To provide empirical evidence from different combinations of the factors in the use of survival analysis, this study built a series of discrete and continuous survival models using secondary data and simulated data. In the first study, using empirical data from the National Longitudinal Survey of Youth 1997 (NLSY97), this study compared analyses results from the two models having different sizes of time metrics. In the second study, by having various specifications with combination of two other factors of censoring proportions and sample sizes, this study simulated datasets to build two models and compared the analysis results. The major finding of the study is that discrete models are recommended in the conditions of large units of time metrics, low censoring proportion, or small sample sizes. Particularly, discrete model produced better outcomes for conditions with low censoring proportion (20%) and small number (i.e., four) of large time metrics (i.e., year) regardless of sample sizes. Close examination of those conditions of time metrics, censoring proportion, and sample sizes showed that the conditions resulted into high hazards (i.e., 0.20). In conclusion, to determine a proper model, it is recommended to examine hazards of each of the time units with the specific factors of time metrics, censoring proportion and sample sizes.
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    The Conceptualization, Utilization, Benefts and Adoption of Learning Objects
    Kim, Sunha (Virginia Tech, 2009-12-07)
    Learning objects have received attention because of their potential to improve current methods of teaching and learning. Despite perceived importance, there has been lack of studies that examine the use of learning objects across various contexts. In response, this study examined the actual use of learning objects and their perceptions among Instructional Design and Technology (IDT) practitioners in U.S. This study was based on the data from 191 IDT practitioners from various sectors, including higher education, business, government, and K-12. The study results contribute to the body of knowledge on learning objects in terms of four areas: conceptualization, utilization, benefits, and adoption. First, the study results should allay the concern that the conceptualization of learning objects focuses too much on technical aspects. IDT practitioners emphasized both technical and learning aspects in conceptualizing learning objects. In conclusion, the present study laid the foundation for a working definition of learning objects. Second, the study showed that IDT practitioners were utilizing learning objects to empower learners to have control over their own learning. The current study identified design strategies that IDT practitioners were frequently using. The most frequently utilized strategy was the provision of concrete, authentic examples and problems. Along with design strategies, this study identified the frequently adopted granularity levels: assets, combined media, one complete instructional unit, lesson or module, and course. Combined media, which consists of content and optional media, was the most frequently utilized granularity level of the five levels. The study provided empirical data to help determine formal design strategies and optimal granularity levels in utilizing learning objects based on the frequent use among IDT practitioners. Third, this study filled the research gap on the benefits of learning objects from an IDT perspective. Study results showed that IDT practitioners were positive about the overall benefits for the ID process, along with reusability and the support for the motivation and interactivity features. However, they were less convinced of the time and cost savings. Generally, IDT practitioners were satisfied with the benefits of learning objects. Fourth, the present study improved the understanding of the adoption status of learning objects. Currently, many of the participants' organizations were adopting or exploring the implementation of learning objects. The adoption of learning objects has a promising future, as IDT practitioners were positive about their organizations' intentions to use learning objects in the future. At the individual level, IDT practitioners were found to use learning objects for their professional role and across various projects. As an adoption factor, IDT practitioners showed the positive reactions to learning objects' perceived usefulness.