• 제목/요약/키워드: confounding

검색결과 370건 처리시간 0.105초

품질실험계획 모형의 특징 및 적용방안 (Implementation and Features for Design of Experiment)

  • 최성운
    • 대한안전경영과학회:학술대회논문집
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    • 대한안전경영과학회 2010년도 춘계학술대회
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    • pp.519-524
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    • 2010
  • The research presents implementation strategy and features for experimental design of quality. The MINITAB models of experimental design classfies by the kinds of factors, orthogonality, blocking, confounding and rotationability. The results discussed in this paper can be easily used for practictioners.

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인과연구에서 중첩편향을 제거하기 위한 공변량선택기준 (Covariate selection criteria for controlling confounding bias in a causal study)

  • ;김지현
    • 응용통계연구
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    • 제29권5호
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    • pp.849-858
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    • 2016
  • 관측 자료를 이용한 인과연구에서 관심 있는 처리변수의 효과가 다른 공변량의 효과와 중첩되지 않도록 조건화할 공변량을 선택하는 것이 중요하다. 인과연구에서의 공변량선택 문제는 공분산분석 모형에서의 변수선택 문제와 다르다는 것을 예를 들어 설명하였다. 그리고 모든 변수들 사이의 인과관계를 파악하지 않고도 적용할 수 있는 실용적인 공변량선택기준에 대해 살펴보았다. VanderWeele과 Shpitser (2011)가 새로운 기준을 제안하면서 새로운 기준이 다른 두 기준보다 나은 성능을 보인다고 주장하였는데, 이 기준에도 한계와 단점이 있음을 예증하였다. 새로운 기준이 완전한 기준은 아니지만 조건을 조금 수정하면 다른 두 기준과 달리 중첩을 제거할 수 있다는 점에서 좀 더 나은 기준이라고 할 수 있다.

A Simple Algorithm for Factorial Experiments in $\rho^N$

  • Donwonn Kim
    • Communications for Statistical Applications and Methods
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    • 제5권2호
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    • pp.353-359
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    • 1998
  • Factorial designs with two-level factors represent the smallest factorial experiments. The system of notation and confounding and fractional factorial schemes developed for the $2^N$system are found in standard textbooks of experimental designs. Just as in the $2^N$ system, the general confounding and fractional factorial schemes are possible in $3^N,5^N$, .... , and $\rho^N$ where $\rho$ is a prime number. Hence, we have the $\rho^N$ system. In this article, the author proposes a new algorithm for constructing fractional factorial plans in the $\rho^N$ system.

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Suppression and Collapsibility for Log-linear Models

  • Sun, Hong-Chong
    • Communications for Statistical Applications and Methods
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    • 제11권3호
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    • pp.519-527
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    • 2004
  • Relationship between the partial likelihood ratio statistics for logisitic models and the partial goodness-of-fit statistics for corresponding log-linear models is discussed. This paper shows how definitions of suppression in logistic model can be adapted for log-linear model and how they are related to confounding in terms of collapsibility for categorical data. Several $2{times}2{times}2$ contingency tables are illustrated.

Survey of the use of statistical methods in Journal of the Korean Association of Oral and Maxillofacial Surgeons

  • Choi, Yong-Geun
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • 제44권1호
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    • pp.25-28
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    • 2018
  • Objectives: This study aimed to describe recent patterns in the types of statistical test used in original articles that were published in Journal of the Korean Association of Oral and Maxillofacial Surgeons. Materials and Methods: Thirty-six original articles published in the Journal in 2015 and 2016 were ascertained. The type of statistical test was identified by one researcher. Descriptive statistics, such as frequency, rank, and proportion, were calculated. Graphical statistics, such as a histogram, were constructed to reveal the overall utilization pattern of statistical test types. Results: Twenty-two types of statistical test were used. Statistical test type was not reported in four original articles and classified as unclear in 5%. The four most frequently used statistical tests constituted 47% of the total tests and these were the chi-square test, Student's t-test, Fisher's exact test, and Mann-Whitney test in descending order. Regression models, such as the Cox proportional hazard model and multiple logistic regression to adjust for potential confounding variables, were used in only 6% of the studies. Normality tests, including the Kolmogorov-Smirnov test, Levene test, Shapiro-Wilk test, and $Scheff{\acute{e}}^{\prime}s$ test, were used diversely but in only 10% of the studies. Conclusion: A total of 22 statistical tests were identified, with four tests occupying almost half of the results. Adoption of a nonparametric test is recommended when the status of normality is vague. Adjustment for confounding variables should be pursued using a multiple regression model when the number of potential confounding variables is numerous.

의료급여 수급권자 확대정책이 예방가능한 입원율에 미친 영향 (The Impact of Medicaid Expansion to include population with low income on the preventable hospitalizations)

  • 신현철;김세라
    • 보건행정학회지
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    • 제20권1호
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    • pp.87-102
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    • 2010
  • The objective of this study were to examine the impact of medicaid coverage expansion policy aimed at improving access to primary care. The case-control study was conducted to compare preventable hospitalization(PH) rate in new medicaid recipients versus national health insurance(NHI) enrollees form 1996 to 2001. Rates of preventable hospitalization associated with ambulatory care sensitive conditions(ACSC) were calculated and standardized by age and sex. Multinomial logit regression model was used to control the confounding factors such as age, gender and charlson comorbidity index Annual PH rates in the new medicaid increased 1.64 times after medicaid expansion, with controling confounding factors. Meanwhile, annual PH rate in the NHI increased 1.68 times during the same period, with adjusting confounding factors. Current findings suggest that the new medicaid PH rate was less likely to rise than NHI PH rate after implementing medicaid expansion. This study is expected to provide policy-relevant evidence of medicaid expansion to include population with low income.

Confounding of Time Trend with Dropout Process in Longitudinal Data Analysis

  • Kim, Ji-Hyun;Choi, Hye-Hyun
    • Communications for Statistical Applications and Methods
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    • 제9권3호
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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.

Logistic Analysis를 이용하여 분석한 인공유산이 속발성불임에 미치는 영향 (The Study of the Influence of Induced Abortion on Secondary Infertility analyzed by Logistic Regression)

  • 이원철
    • Journal of Preventive Medicine and Public Health
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    • 제15권1호
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    • pp.179-186
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    • 1982
  • The methods controlling the confounding factors were discussed using the data of secondary infertility with induced abortion. Mantel-Haenszel method and logistic model were applied in the analysis to find out which factors were confounding and/or effect modification variables. In the logistic analysis, the main effect of induced abortion, spontaneous abortion, age and interaction effect between induced abortion and spontaneous abortion were chosen as independent variables being regressed into logistic functions. Spontaneons abortion was interpreted as a potential confounder and at the same time potential effect modifier and age was interpreted as potential confounder. Spontaneous abortion was shown to be more important influencing factor than age to the secondary infertility. In the course of logistic analysis, the problem of parameter estimation and hypothesis testing, assessing the fitness of a model, and selection of the best model were briefly explained. For the program of logistic model, FUNCAT Procedure of SAS package was chosen.

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한국 성인에서 간접흡연노출과 우울증상 간의 상관관계 (Association between Secondhand Smoke Exposure and Depressive Symptoms among Korean Adults)

  • 진선권;한규만;남민;장지순
    • 생물정신의학
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    • 제27권2호
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    • pp.101-111
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    • 2020
  • Objectives The aim of this study is to investigate the association between secondhand smoke (SHS) exposure and depressive symptoms among Korean adults. This study also explored the mediating role of self-rated health (SRH) and perceived usual stress (PUS) in the association between depressive symptoms, suicidal ideation and SHS exposure. Methods Data from the Korea National Health and Nutrition Examination Surveys (KNHANES) in 2014 and 2016 was analyzed for 10539 participants aged 19 years or older. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated in the logistic regression analysis with adjustment for the potential confounding factors. We also adopted the mediation analysis method by Hayes and Preacher. Results After adjusting for the potential confounding factors, SHS at home and at public places were associated with depressive symptoms and suicidal ideation among non-smokers. After adjusting for the potential confounding factors, SHS at home and at public places was associated with depressive symptoms and suicidal ideation among non-smokers. Meanwhile SHS at workplaces was associated with depressive symptoms among former smokers and with suicidal ideation among current smokers. There was an additive effect of SHS on depressive symptoms only among non-smokers. SRH mediated the association between SHS and depressive symptoms and suicidal ideation among non-smokers. We did not observe any significant mediating effect of SRH nor PUS on the association between SHS and depressive symptoms among former and current smokers. Conclusions SHS may be associated with depressive symptoms and suicidal ideation in Korean adults. Our study elucidated how SHS interacted with depressive symptoms among non-smokers through the mediation by SRH.

청소년의 인터넷 중독현상과 자기통제기대의 구조적 경로모형에 관한 연구 (The Structural Path Model of Adolescents′ Internet Addiction and Expected Self-Control)

  • 박재성
    • 보건교육건강증진학회지
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    • 제21권3호
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    • pp.1-17
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    • 2004
  • The purpose of this study is to evaluate the roles of expected self-control and expected self-control results in explaining adolescents' Internet addiction. In the study model, expectations of self-control and self-control results directly determine Internet addiction and Internet use time meditates the impacts of expectations of self-control and self-control results on Internet addiction. The study subjects are 1,080 middle and high school students in Busan. Stratified cluster sampling is applied by school type and school year. The response rate is 96%(l,037cases). This study develops the scales of expected self-control and expected self-control results. The scales of Internet addiction are devised by using the concept of functional dependency such as salience, withdrawal symptoms, mood modification, tolerance, relapse, and conflict. For verifying the study model, path analysis and multiple regression models are applied for identifying path significants and evaluating confounding effects of control variables, respectively. Moreover, multi partial F-test is performed for selecting the best regression model. Expected self-control is a significant determinant of Internet addiction and Internet use time that also significantly explains Internet addiction. The total effect of expected self-control towards Internet addiction is -.95. The total effect is comprised with the direct effect (-.71) and the indirect effect(-.24). In this result, the direct effect refers a curative effect since expected self-control directly reduces the level of Internet addiction, and the indirect effect refers a preventive effect because self-control can reduce time of Internet use that is a direct determinant of Internet addiction. In the test of the confounding effects of control variables, there are no confounding effects in the models of multiple regression. It implies a robustness of the study model as regards control variables. In conclusion, improving adolescents' expected self-control can control Internet addiction level. This finding implies that a health promotion program for improving expected self-control can be a cost effective method compared to other approaches.