• Journal of the Korean Statistical Society
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• v.9 no.2
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• pp.145-172
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• 1980

Draper and Lawrence (1965a) have given mixture designs for three factors when all the mixture components can vary on the entire factor space so that the region of interest is an equilateral triangle in two dimensions. In this paper their work is extended to the cases when the region of interest is an echelon, parallelogram, pentagon or hexagon, because of the restirctions imposed on some or all of the mixture components. The principles used in the choice of appropriate designs are those originally introduced by Box and Draper(1959). It is assumed that a response surface equation of first order is fitted, but there is a possibility of bias error due to presence of second order terms in the true model. Minimum bias designs for several cases of restricted regions of interest are illustrated.

• Journal of the military operations research society of Korea
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• v.29 no.2
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• pp.13-25
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• 2003

The lack of consideration for statistical properties in Taguchi's three­level linear graphs is rectified. We propose a new set of linear graphs for the three­level orthogonal arrays according to the maximum resolution criterion. In the presence of two­factor interactions however, the serious bias of all the estimated effects as well as the estimated variance shows that these designs should not be employed. The various alternative designs are discussed.

• Child Health Nursing Research
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• v.23 no.3
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• pp.300-311
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• 2017

Purpose: There are many forest and outdoor programs being offered but systematic reviews of effects are lacking. This study was done to identify content, format, and strategies of forest therapy programs for elementary school students. Methods: Literature search using keywords in English and Korean was performed using 6 electronic databases in December 2016. Search participants were elementary school students and interventions conducted in the forest. Seventeen forest therapy studies were selected for evaluation. Risk of Bias Assessment tool for non-randomized study was used for quality assessment. Results: All studies were quasi-experimental designs. Forest therapy programs included various activities in forests such as experience of five senses, meditation in the forest, walking in the forest, ecological play, observation of animals and insects. All studies used psychosocial health variables and forest healing programs had positive effects on sociality, depression, anxiety, self-esteem, stress, aggression, anger, and school adjustment. Limitations of these studies were vague reporting of the study, lack of ethical review and rigorous research designs. Conclusion: Forest therapy for elementary school child can be an effective way to improve psychosocial health. Future studies with rigorous study designs are needed to assess long-term effects of forest therapy on physical and psychosocial health.

• Communications for Statistical Applications and Methods
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• v.26 no.2
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• pp.175-189
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• 2019

The problem of the estimation of quantitative sensitive variable using the item sum technique (IST) on successive occasions has been discussed. IST difference, IST regression, and IST general class of estimators have been proposed to estimate quantitative sensitive variable at the current occasion in two occasion successive sampling. The proposed new estimators have been elaborated under Trappmann et al. (Journal of Survey Statistics and Methodology, 2, 58-77, 2014) as well as Perri et al. (Biometrical Journal, 60, 155-173, 2018) allocation designs to allocate long list and short list samples of IST. The properties of all proposed estimators have been derived including optimum replacement policy. The proposed estimators have been mutually compared under the above mentioned allocation designs. The comparison has also been conducted with a direct method. Numerical applications through empirical as well as simplistic simulation has been used to show how the illustrated IST on successive occasions may venture in practical situations.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.48 no.5
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• pp.259-266
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• 2022

The relationship between obstructive sleep apnea (OSA) and diverse types of pain conditions have been proposed. However, no consensus on the relationship between OSA and painful temporomandibular disorders (TMDs) has been established. Therefore, this systematic review has been conducted to review the existing literatures and provide comprehensive synthesis of such literatures about OSA and painful TMDs using the evidence-based methodology. A literature search was conducted using two electronic databases, Scopus, and PubMed. Risk of bias was assessed using the risk-of-bias assessment tool for non-randomized study version 2.0. A total of 158 articles were screened from the initial search and eventually, 5 articles were included in this systematic review. One study adopted both the longitudinal prospective cohort and case-control designs and other 4 articles adopted the cross-sectional design. Two studies employed polysomnography (PSG) for the diagnosis of OSA and mentioned the results from the PSG. All cross-sectional studies demonstrated higher OSA prevalence among patients with TMD, and one cohort study suggested OSA as a risk factor for TMD. OSA appears to have potential influences on the development of TMD; however, the role of TMD in the development of OSA remains to be unknown owing to the lack of high-quality evidences.

• Journal of Korean Academy of Nursing
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• v.47 no.2
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• pp.143-163
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• 2017

Purpose: This study was a systematic review and meta-analysis designed to investigate effects of psychoeducational intervention for cancer survivors. Methods: Ten databases were searched. Two reviewers independently performed the selection of the studies, data extraction and assessment. The risk of bias was assessed using Cochrane Collaboration's tool. To estimate the effect size, meta-analysis of the studies was performed using Comprehensive Meta-Analysis and RevMan programs. Results: Of 18,781 publications identified, 35 met inclusion criteria, and 25 studies were used to estimate effect size of psychoeducational intervention. Effect sizes (standardized mean difference [SMD]) were heterogeneous and random effects models were used in the analyses. Psychoeducational intervention was effective for quality of life (n=2,410, ES=0.23; 95% CI: 0.09~0.37), coping and self-efficacy (n=179, ES=0.68; 95% CI: 0.26~1.11), anxiety (n=1,786, ES=-0.26; 95% CI: -0.37~-0.15), depression (n=1,910, ES=-0.28; 95% CI: -0.37~-0.18), and psychological distress (n=2,242, ES=-0.31; 95% CI: -0.46~-0.17). Subgroup analysis showed that counseling was the most effective intervention for quality of life, and behavioral therapy was an effective intervention for all positive and negative outcomes. Publication bias was not detected except for psychological distress. Conclusion: Psychoeducational intervention appears to be effective in improving quality of life and coping and self-efficacy, and it is effective in reducing psychological symptoms in cancer survivors. Behavioral therapy, especially, is commonly effective in improving psychosocial outcomes. However, low-quality evidence, variability in the designs of existing studies, and publication bias suggest that additional high-quality trials should be conducted in the future.

• Journal of the Korean Statistical Society
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• v.32 no.3
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• pp.245-259
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• 2003

The 2-way balanced one-level rotation design has been discussed (Park et al., 2001), where the 2-way balancing is done on interview time in monthly sample and rotation group. We extend it to 3-way balanced multi-level design to obtain more information of the same sample unit for one or more previous months. The 3-way balancing is accomplished not only on interview time in monthly sample and rotation group but also on recall time as well. The 3-way balancing eliminates or reduces any bias arising from unbalanced interview time, rotation group and recall time, and all rotation groups are equally represented in the monthly sample. We present the rule and rotation algorithm which guarantee the 3-way balancing. In particular, we specify the necessary and sufficient condition for the 3-way balanced multi-level rotation design.

• Communications for Statistical Applications and Methods
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• v.30 no.4
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• pp.403-410
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• 2023

Two-Phase sampling, which was first introduced by Neyman (1938), has various applications in different forms. Variance estimation for two-phase sampling has been an important research topic because conventional variance estimators used in most softwares are not working. In this paper, we considered a variance estimation for two-phase sampling in which stratified two-stage cluster sampling designs are used in both phases. By defining a conditionally unbiased estimator of an approximate variance estimator, which is calculable when all elements in the first phase sample are observed, we propose an explicit form of variance estimator of the double expanded estimator for a two-phase sample. A small simulation study shows the proposed variance estimator has a negligible bias with small variance. The suggested variance estimator is also applicable to other linear estimators of the population total or mean if appropriate residuals are defined.

• Child Health Nursing Research
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• v.24 no.3
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• pp.263-273
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• 2018

Purpose: This study analyzes meaning-centered intervention studies conducted in Korea and abroad to compare and confirm their characteristics and results. Methods: A literature search using keywords in English and Korean was performed using nine electronic databases in December 2017. Search participants included adolescents, and interventions conducted in meaning-centered intervention studies were selected for evaluation. A Risk of Bias Assessment tool for non-randomized studies was used for quality assessment. Results: All studies were based on quasi-experimental designs. The semantic intervention included topics such as freedom, choice, responsibility, pain, death, finding value of life, purpose and meaning of life, and becoming a master of my life. All studies used logotherapy, and included meaningful interventions that influenced the meaning and purpose of the life of adolescents. The life satisfaction of adolescents changed significantly when there is a positive and open relationship with their parents. Therefore, an educational program for parents based on meaning therapy is desperately needed. Conclusion: Meaning-centered interventions were found to be effective interventions for exploring the meaning of life not only for adolescents with problems but also for healthy youth, and as such could be used as basic data for the development of an appropriate intervention for enhancing their life.

• Survey Research
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• v.7 no.2
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• pp.53-69
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• 2006

Weights can be made and imposed in both sample design stage and analysis stage in a sample survey. While in design stage weights are related with sample data acquisition quantities such as sample selection probability and response rate, in analysis stage weights are connected with external quantities, for instance population quantities and some auxiliary information. The final weight is the product of all weights in both stage. In the present paper, we focus on the weight in analysis stage and investigate the effect of such weights imposed on the weighted mean when estimating the population mean. We consider a finite population with a pair of fixed survey value and weight in each unit, and suppose equal selection probability designs. Under the condition we derive the formulas of the bias as well as mean square error of the weighted mean and show that the weighted mean is biased and the direction and amount of the bias can be explained by the correlation between survey variate and weight: if the correlation coefficient is positive, then the weighted mein over-estimates the population mean, on the other hand, if negative, then under-estimates. Also the magnitude of bias is getting larger when the correlation coefficient is getting greater. In addition to theoretical derivation about the weighted mean, we conduct a simulation study to show quantities of the bias and mean square errors numerically. In the simulation, nine weights having correlation coefficient with survey variate from -0.2 to 0.6 are generated and four sample sizes from 100 to 400 are considered and then biases and mean square errors are calculated in each case. As a result, in the case or 400 sample size and 0.55 correlation coefficient, the amount or squared bias of the weighted mean occupies up to 82% among mean square error, which says the weighted mean might be biased very seriously in some cases.