• Journal of Applied Reliability
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• v.6 no.3
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• pp.225-237
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• 2006

This paper proposes a method of modelling the informative dropouts with QoL(quality of life) in survival analysis. QoL is the index to measure the health related quality of life of a patient who got some treatments for a disease. Dropouts are prevalent occurrences on longitudinal study They are commonly dependent to the QoL of patients, that is, severe disease or death and called informative dropouts. Modelling the mechanism of dropouts could achieve the more accurate inference for survival analysis. A likelihood method is proposed to estimate the survival parameter and test the patterns of dropouts.

• Communications for Statistical Applications and Methods
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• v.9 no.3
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• pp.703-713
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• 2002

In longitudinal studies, outcomes are repeatedly measured over time for each subject. It is common to have missing values or dropouts for longitudinal data. In this study time trend in longitudinal data with dropouts is of concern. The confounding of time trend with dropout process is investigated through simulation studies. Some simulation results are reported for binary responses as well as continuous responses with patterns of dropouts varying. It has been found that time trend is not confounded with random dropout process for binary responses when it is estimated using GEE.

• Electrical & Electronic Materials
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• v.8 no.5
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• pp.633-639
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• 1995

Dropouts in magnetic media are a primary quality deficiency which is detrimental to magnetic signal quality and thus the major impediment to error-free recording, especially in high density digital recorders. The specific form of defects and causes found to be responsible for signal dropouts occurring in magnetic tape were studied. Dropout occurred when the RF signal falls to low level due to the various types of surface defects. However, the fall in the level of the RF signal in gravure roll coated tapes was most often caused by foreign particles adhering to the magnetic tape. It was also shown from the present study that scattered particles trapped under the tape surface or put on the top can lift it as it crosses the head, creating a spherical tent shaped defect and causing a temporary signal drop. Dropout producing substances were identified through optical and microchemical analyses. The results were correlated with measured electrical signal losses combined with analytical microscopy to clarify source identification of defects.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1731_1732
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• 2009

This paper presents a stability analysis of networked control systems with packet dropouts. The packet dropouts are modeled as a linear function of the stochastic variable satisfying Bernoulli random binary distribution and weighted moving average (WMA). The observer based controller scheme is designed to exponentially mean square stabilize the NCS. Simulation results is provided to show the applicability of the proposed method.

• Communications for Statistical Applications and Methods
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• v.15 no.3
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• pp.353-365
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• 2008

The sample size in a clinical trial is determined by the hypothesis, the variance of observations, the effect size, the power and the significance level. Dropouts in clinical trials are inevitable, so we need to consider dropouts on the determination of sample size. It is common that some proportion corresponding to the expected dropout rate would be added to the sample size calculated from a mathematical equation. This paper proposes new equations for calculating sample size dealing with dropouts. Since we observe data longitudinally in most clinical trials, we can use a last observation to impute for missing one in the intention to treat (ITT) trials, and this technique is called last observation carried forward(LOCF). But LOCF might make deviations on the assumed variance and effect size, so that we could not guarantee the power of test with the sample size obtained from the existing equation. This study suggests the formulas for sample size involving information about dropouts and shows the properties of the proposed method in testing equality of means.

• 한국정보컨버전스학회:학술대회논문집
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• 2008.06a
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• pp.89-92
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• 2008

This study analyzed the status and causes for the dropouts of college based on the survey conducted among 14,210 freshmen attending D College, other than the supernumerary special selection, from 2001 through 2005. A significant difference was shown in all items of general characteristics. The dropout rate of women, generally selected and general high school graduated were higher than for men, specially selected and special high school graduated, respectively. The most dropouts were due to Not Return(40.16%), followed by Unenrolled(32.98%), Voluntary Leave(26.05%) and Expelled(0.81%) in order. In the distribution of the central tendency values measured from the entire subjects. the high school records and the days of absence showed a positive skewness. while the college records showed a negative skewness with the data mostly around a higher grade. The standard deviation indicating that the dropouts got the scores higher than those of the continuing students demonstrated that there was relatively insignificant difference in scores between two groups.

• Journal of Fashion Business
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• v.14 no.1
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• pp.184-197
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• 2010

This study was conducted by the questionnaires to 323 undergraduate students in fashion related departments. Questionnaires were designed to ask total 23 questions including possibility of halfway dropouts, establishment of goals, self-improvement, entrance motives, satisfaction ratings of academic subjects, job prospects and path planning, amelioration of ways to instruct, desires for the integrated lessons and intense academic courses, wishes of field project education carrying out tasks, desired lecturers, and others. Results in this research were summarized as follows. To begin with, it was appeared that respondents with possibility of halfway dropouts showed considerable percentage (25.4%) and the reasons left out were various including joining the army, the poor economic conditions in family, a major not corresponding with one's aptitude. Secondly, in the extent of establishing goals and improving oneself, there was the difference between people with possibility of halfway dropouts and people without that, and it was judged that the extent of establishing goals and improving oneself as good parameters could explain halfway omission. Thirdly, the ways to teach for getting classes interesting were to make instruction according to one's capabilities, to progress systematically, and to take lessons with specific goals. Fourth, many respondents answered to want the integrated lessons, intense academic courses, and field project education carrying out tasks. Fifth, an overwhelming majority of respondents hoped instructors with a outstanding ability in business. For improvement of the ways to instruct and the role of professors, it is suggested as follows. First, students are given intelligible lessons focused on fundamental subjects fitted to their levels and also need gradual intense academic courses classified by their way directions and interests. Second, creative and individualized teaching methods depending on the majors and levels are developed to help students have strong interest in schoolwork. Third, professors are constantly to learn practical techniques and skills related to industries in step with the education goals of college. Fourth, it is desirable to adopt instructors with practical business talents rather than theoretical capabilities.

• Journal of the Korea society of information convergence
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• v.1 no.1
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• pp.47-54
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• 2008

This study analyzed the status and causes for the dropouts of college based on the survey conducted among 14,210 freshmen attending D College, other than the supernumerary special selection, from 2001 through 2005. A significant difference was shown in all items of general characteristics. The dropout rate of women, generally selected and general highschool graduated were higher than for men, specially selected and special high school graduated, respectively. The most dropouts were due to Not Return(40.16%), followed by Unenrolled(32.98%), Voluntary Leave(26.05%) and Expelled(0.81%) in order. In the distribution of the central tendency values measured from the entire subjects, the high school records and the days of absence showed a positive skewness, while the college records showed a negative skewness with the data mostly around a higher grade. The standard deviation indicating that the dropouts got the scores higher than those of the continuing students demonstrated that there was relatively insignificant difference in scores between two groups. It was demonstrated that both the high school records and the days of absence affected the dropout. The lower the high school records were, and the more the days of absence were, the more influence both items had on the dropout. The influence degree of each item was similar. Lower the scores were in terms other than the first term in the freshmen year, the more influence it had on the dropout. The most dropouts were influenced by the scores of the freshmen year, followed by the credits of the second term, the scores of the first term, the scores of the second term, and the credits of the first term in the freshmen year. Among the general characteristic items, the most dropouts were influenced by the course of study, followed by the gender. The effect of other items was insignificant.

• Korean Journal of Child Studies
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• v.30 no.6
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• pp.391-403
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• 2009

This study examined the concept and status, research issues, and pragmatic and policy issues of school-dropout adolescents. As the number of school-dropout adolescents has been increasing in Korea since 2006, more attentions have been given to these adolescents academically, intervention and policy-wise. Some of the research topics on them include types of school-dropouts, their socio-environmental factors, and reasons for the increase of school-dropouts. In reality, the government is required to provide them with opportunities to cope with their dropping out of schools by preparing the career guidance for them and to resolve the issues of their returning to or continuing in school education and their welfare.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.12
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• pp.5989-5994
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• 2012

Background: There is little information on longitudinal patterns of participation in faecal occult blood test (FOBT) based colorectal cancer (CRC) screening or on demographic or behavioural factors associated with participation in re-screening. The lack of an agreed system for describing participatory behaviour over multiple rounds also hampers our ability to report, understand and make use of observed associations. Our aims were to develop a system for describing patterns of participatory behaviour in FOBT-based CRC screening programs and to identify factors associated with particular behavioural patterns. Methods: A descriptive framework was developed and applied to a data extract of screening invitation outcomes over two rounds of the NBCSP. The proportion of invitees in each behaviour category was determined and associations between behaviour patterns and demographic and program factors were identified using multivariate analyses. Results: We considered Re-Participants, Dropouts, Late Entrants and Never Participants to be the most appropriate labels for the four possible observed participatory categories after two invitation rounds. The screening participation rate of the South Australian cohort of the NBCSP remained stable over two rounds at 51%, with second round Dropouts (10.3%) being balanced by Late Entrants (10.5%). Non-Participants comprised 38.7% of invitees. Relative to Re-Participants, Dropouts were older, more likely to be female, of lower SES, had changed their place of residence between offers had a positive test result in the first round. Late Entrants tended to be in the youngest age band. Conclusions: Specific demographic characteristics are associated with behavioural sub-groups defined by responses to 2 offers of CRC screening. Targeted group-specific strategies could reduce dropout behaviour or encourage those who declined the first invitation to participate in the second round. It will be important to keep first round participants engaged in order to maximise the benefit of a CRC screening program.