• Journal of applied mathematics & informatics
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• 제14권1_2호
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• pp.377-386
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• 2004

A technique that provides prediction intervals based on a model called an empirical linear model is discussed. The technique, high-dimensional empirical linear prediction (HELP), involves principal component analysis, factor analysis and model selection. HELP can be viewed as a technique that provides prediction (and confidence) intervals based on a factor analysis models do not typically have justifiable theory due to nonidentifiability, we show that the intervals are justifiable asymptotically.

• International Journal of Reliability and Applications
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• 제3권1호
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• pp.37-50
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• 2002

Simultaneous estimation of accuracy and probability corresponding to a prediction interval is considered in this study. Traditional application of confidence interval forecasting consists in evaluation of interval limits for a given significance level. The wider is this interval, the higher is probability and the lower is the forecast precision. In this paper a measure of stochastic forecast accuracy is introduced, and a procedure for balanced estimation of both the predicting accuracy and confidence probability is elaborated. Solution can be obtained in an optimizing approach. Suggested method is applied to constructing confidence intervals for parameters estimated by normal and t distributions

• 대한수학교육학회지:수학교육학연구
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• 제26권4호
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• pp.755-768
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• 2016

교사의 수업자신감은 학생들의 성취도 향상에 영향을 줄 뿐만 아니라 교사의 직업 생활의 질을 높이는 데도 중요한 변인임에도 불구하고, TIMSS 결과에서는 다른 국가에 비해 우리나라 중등 수학 교사의 수업자신감이 낮은 것으로 나타났다. 교사들의 수업자신감을 높이기 위한 방안을 탐색하고자 본 연구에서는 교사경력, 수업준비도, 교사협력, 수업제한의 네 가지 맥락변인이 우리나라 중등 수학 교사의 수업자신감에 미치는 영향과 이 변인들이 수업자신감의 변화에 대해 갖는 설명력을 살펴보았다. 분석 결과 네 가지 예측 변인을 투입했을 때 수업준비도, 교사협력, 수업제한의 세 가지 변인이 수업자신감에 영향을 주고, 수업자신감의 변화에 대한 설명력의 경우 다른 변인이 합성되지 않은 수업준비도의 고유 효과가 가장 큰 것으로 나타났다.

• 한국수학교육학회지시리즈A:수학교육
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• 제56권2호
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• pp.147-160
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• 2017

The purpose of this study was to examine (1) if sociocultural factors that are known to influence gender gap in mathematics achievement are gender equitable for Singaporean eighth grade students, (2) if there is a higher level of gender equitability in students' attitudes towards mathematics and (3) how sociocultural factors influence mathematics achievement for Singaporean eighth grade students. This study is based on 5,923 Singaporean eighth grade students who participated in TIMSS 2011 assessment. The study found that there were no statistically significant gender differences in 'parental involvement in education' and 'teacher efficacy.' There were no statistically significant gender differences in students' attitudes of 'like learning mathematics,' and 'value learning mathematics'. A significant gender difference was identified for the attitude of 'confident with mathematics.' The boys displayed a higher level of confidence in mathematics than the girls consistent with other study findings for Asian students. The degree of effect from 'parental involvement in education,' 'teacher efficacy,' and 'confident with mathematics' on mathematics achievement are found to be stronger for girls than boys. The finding implies that girls' mathematics achievement can benefit from having more positive encouragement and involvement of parents and teachers and strengthening confidence in mathematics.

• Communications for Statistical Applications and Methods
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• 제3권2호
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• pp.29-36
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• 1996

In regression model with nested error structure interval estimations about variability on different stages are proposed. This article derives an approximate confidence interval on the variance in the first stage and an exact confidence interval on the variance in the second stage in two stage regression model. The approximate confidence interval is vased on Ting et al. (1990) method. Computer simulation is procided to show that the approximate confidence interval maintains the stated confidence coeffient.

• 충청수학회지
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• 제14권2호
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• pp.47-54
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• 2001

Let {Xn, n = 1,2,${\cdots}$} be i.i.d. random variables with the only unknown parameters mean ${\mu}$ and variance a ${\sigma}^2$. We consider a sequential confidence interval C1 for the mean with coverage probability 1-${\alpha}$ and expected length of confidence interval $E_{\theta}$(Length of CI)/${\mid}{\mu}{\mid}{\leq}k$ (k : constant) and give some asymptotic properties of the stopping time in various limiting situations.

• Communications for Statistical Applications and Methods
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• 제23권4호
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• pp.269-285
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• 2016

In this paper, a simple step-stress accelerated life test (ALT) under progressive type-II censoring is considered. Progressive type-II censoring and accelerated life testing are provided to decrease the lifetime of testing and lower test expenses. The cumulative exposure model is assumed when the lifetime of test units follows an extension of the exponential distribution. Maximum likelihood estimates (MLEs) and Bayes estimates (BEs) of the model parameters are also obtained. In addition, a real dataset is analyzed to illustrate the proposed procedures. Approximate, bootstrap and credible confidence intervals (CIs) of the estimators are then derived. Finally, the accuracy of the MLEs and BEs for the model parameters is investigated through simulation studies.

• Communications for Statistical Applications and Methods
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• 제8권1호
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• pp.127-135
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• 2001

In this paper, we consider a simple method for testing the assumption of independent censoring on the basis of a Cox proportional hazards regression model with a time-dependent covariate. This method involves a two-stage sampling in which a random subset of censored observations is selected and followed-up until their true survival times are observed. Lee and Wolfe(1998) proposed an adjusted estimate of the survivor function for the dependent censoring under a proportional hazards alternative. This paper extends their result to obtain a bootstrap confidence interval for the adjusted survivor function under the dependent censoring. The proposed procedure is illustrated with an example of a clinical trial for lung cancer analysed in Lee and Wolfe(1998).

• Communications for Statistical Applications and Methods
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• 제27권6호
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• pp.625-639
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• 2020

The gamma distribution is a flexible right-skewed distribution widely used in many areas, and it is of great interest to estimate the probability of a random variable exceeding a specified value in survival and reliability analysis. Therefore, the study develops a fixed-accuracy confidence interval for P(X > c) when X follows a gamma distribution, Γ(α, β), and c is a preassigned positive constant through: 1) a purely sequential procedure with known shape parameter α and unknown rate parameter β; and 2) a nonparametric purely sequential procedure with both shape and rate parameters unknown. Both procedures enjoy appealing asymptotic first-order efficiency and asymptotic consistency properties. Extensive simulations validate the theoretical findings. Three real-life data examples from health studies and steel manufacturing study are discussed to illustrate the practical applicability of both procedures.

• 한국수학교육학회지시리즈A:수학교육
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• 제55권3호
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• pp.317-334
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• 2016

Knowledge and data interpretation on statistical estimation was important to have statistical literacy that current curriculum was said not to satisfy. The author investigated mathematics teachers' MKT on statistical estimation concerning interpretation of confidence interval by using questionnaire and interview. SMK of teachers' confidence was limited to the area of textbooks to be difficult to interpret data of real life context. Most of teachers wrongly understood SMK of interpretation of confidence interval to have influence upon PCK making correction of students' wrong concept. SMK of samples and sampling distribution that were basic concept of reliability and confidence interval cognized representation of samples rather exactly not to understand importance and value of not only variability but also size of the sample exactly, and not to cognize appropriateness and needs of each stage from sampling to confidence interval estimation to have great difficulty at proper teaching of statistical estimation. PCK that had teaching method had problem of a lot of misconception. MKT of sample and sampling distribution that interpreted confidence interval had almost no relation with teachers' experience to require opportunity for development of teacher professionalism. Therefore, teachers were asked to estimate statistic and to get confidence interval and to understand concept of the sample and think much of not only relationship of each concept but also validity of estimated values, and to have knowledge enough to interpret data of real life contexts, and to think and discuss students' concepts. So, textbooks should introduce actual concepts at real life context to make use of exact orthography and to let teachers be reeducated for development of professionalism.