多目标抽样的区间估计方法

实践中经常会碰到一些多目标抽样的问题,由于总体单位在各个目标上的差异往往很大,给抽样调查的设计、目标量的估计、样本容量的确定以及抽样误差的控制等方面带来了困难,因而如何兼顾各个目标的要求是多目标抽样研究的难题之一。笔者试提出一种多目标抽样的区间估计方法,希望能够从一个总体的角度对总体参数的置信区间进行测量,从而避免各个目标     

二项分布下基于鞍点逼近的总体成数置信区间的构造

面对总体成数置信区间的估计问题,可以采用二项分布下基于鞍点逼近的方法来构造总体成数的置信区间,这种方法为总体成数的区间估计提供了一种新的途径,将其和传统的区间估计方法比较,即正态近似法和枢轴量法进行比较。蒙特卡洛模拟和实例分析的结果为:在几种不同的置信区间构造方法中,小样本情况下,鞍点逼近方法构造的总体成数的置信区间长度相对较短,覆盖率最接近名义水平;大样本下,鞍点逼近方法整体表现最优。因此,可以得到鞍点逼近法对总体成数置信区间的估计较为精确,尤其是小样本情况下更为适用的结论。     

同总体二比例差的抽样估计

同总体二比例差的抽样估计赵俊康一、问题的提出总体比例（即总体中具有某一村征的单位数占全部总体单位数的比重）是抽样调查中的重要目标量之一。在比例估计中,根据研究目的,除了需要估计具有不同特征的单位数的比例之外,有时候还需要对这些比例间的差作出估计,尤其...     

关于参数的最短置信区间的数值计算

文章研究了在总体均值未知时,σ2及σ在置信水平为0.90和0.95下的最短置信区间,并对通常方法和本文所用方法得到的置信区问进行了对比分析.在一定置信水平下,参数最短置信区间的求解归结为一种非线性规划问题,并用运筹学的优化方法证明了这种分布的最短置信区间所应满足的条件.又给出了参数在置信水平为0.90和0.95下的最短置信区间.通过计算比较,得出结论:在小样本的情况下,用文章所求的置信区间作为未知参数的区间估计将会使估计精度得到显著的提高.     

层次Bayes模型在抽样调查中的应用

在抽样调查中,经常需要估计总体中具有某一特征的个体单位的比例p,当我们所关心的这个比例很小,或者是样本量n很小时,通过样本得到的估计就不是很好。文章构造了层次Bayes模型,利用参数和超参数的先验分布推导出总体的后验分布,通过随机模拟了解比例p的大致分布情况。这种随机模拟的方法计算速度很快,而且准确性也较高。     

随机化问卷模型设计分析

引言:所谓敏感性问题。是指与个人或单位的隐私或利益有关而不便于向外界透漏的问题,例如:你行贿吗?你吸毒吗?你偷税吗?等等问题。对于这些问题,如果进行直接抽样调查,估计敏感属性在总体中比例时,由于涉及到个人的隐私,或有的问题本身涉及到违法,被调查者往往会拒     

辅助信息在二重抽样中的应用

一、问题的提出在抽样理论中,我们往往会利用研究总体的某些辅助信息来提高估计的精度。比如,在抽样设计阶段,可以利用辅助信息进行不等概率抽样或者分层抽样;在估计阶段,可以利用辅助信息进行比率估计和回归估计。但是,在有些情况下,这些关于总体的辅助信息在抽样之前并不知道     

辅助信息在抽样调查中的应用

一、辅助信息及其种类 在抽样调查中，调查指标的样本信息是估计总体目标量必不可少的信息，我们称其为基本信息。由于样本是总体的一部分，抽样又是按照一定概率进行的，故样本提供的是不全面的且带有随机干扰的信息。这就是说，基本信息不仅量极其有限，而且在反映总体特征时常常伴有不可消除的偏差，这就必然使估计量精度受到一定限制。 在许多情况下，我们在抽样调查之前对总体及抽样单元并非一无所知，往往是事先掌握某些可资利用的总体信息及抽样单元信息，而在抽样调查中除了获得调查指标的样本信息外，常可伴随获得其它可资利用的样…     

总体比例的区间估计和样本量的确定

通过平移计分置信区间中心点,修正和改善其覆盖概率的统计性能,获取抽样总体比例估计的置信区间。对于放回抽样以及总体容量N较大的不放回抽样,平移系数建议都取0.02 z4;对于较小N∈[50,1000]的不放回抽样,平移系数建议取0.024 z4。基于置信区间,给出了相应的明显优于传统的样本量公式。     

连续性抽样调查中总体均值的估计

在连续性抽样调查中,利用前期信息和辅助信息可以大大提高估计精度,但是以往的估计量大多假设辅助信息总体均值已知,文章介绍一种在连续性抽样调查中,辅助信息总体均值未知的情况下,通过两阶段抽样,利用轮换样本方法和辅助变量信息,对总体均值进行估计的新的估计方法,并将新提出的估计量与原有的估计量进行比较,发现其精度更高,而且有利于减少调查成本。     

Sample Sizes in the Interval Estimation of the Correlation Coefficient

An expression is derived for the maximum length of the interval estimator of the correlation coefficient, p, under bivariate normal assumptions. The prespecification of this minimum attainable precision and the confidence level results in an expression for the sample size required. An approximate expression for the sample size is proposed and is numerically shown to be as good as or better than that based on the Fisher's Z transformation.     

Sample Sizes and the Central Limit Theorem: The Poisson Distribution as an Illustration

Poisson distributions are often used to show that the central limit theorem is valid even for discrete and for highly skewed distributions. It is not so commonly appreciated that they can also be used to demonstrate that, in some cases, very large sample sizes may not be enough to invoke the theorem. Binomial distributions can be used in a similar manner.     

Sample Size Calculation and Blinded Sample Size Recalculation in Clinical Trials Where the Treatment Effect is Measured by the Relative Risk

In clinical trials with binary endpoints, the required sample size does not depend only on the specified type I error rate, the desired power and the treatment effect but also on the overall event rate which, however, is usually uncertain. The internal pilot study design has been proposed to overcome this difficulty. Here, nuisance parameters required for sample size calculation are re-estimated during the ongoing trial and the sample size is recalculated accordingly. We performed extensive simulation studies to investigate the characteristics of the internal pilot study design for two-group superiority trials where the treatment effect is captured by the relative risk. As the performance of the sample size recalculation procedure crucially depends on the accuracy of the applied sample size formula, we firstly explored the precision of three approximate sample size formulae proposed in the literature for this situation. It turned out that the unequal variance asymptotic normal formula outperforms the other two, especially in case of unbalanced sample size allocation. Using this formula for sample size recalculation in the internal pilot study design assures that the desired power is achieved even if the overall rate is mis-specified in the planning phase. The maximum inflation of the type I error rate observed for the internal pilot study design is small and lies below the maximum excess that occurred for the fixed sample size design.     

A Note on Sample Size Determination for the Estimation of the Mean Vector of a Multivariate Population

In this article, we present a straightforward Bonferroni approach for determining sample size for estimating the mean vector of a multivariate population under two scenarios: (1) a pre-specified overall confidence level is desired; and (2) a pre-specified confidence level needs to be guaranteed for each individual variable. It is demonstrated that correlation between variables helps reduce the sample size. The formula to calculate the reduced sample size is derived. A binormal example is presented to illustrate the effect of correlation on sample size reduction for various values of the correlation coefficient.     

Sample size needed to get given ratio of endpoints for confidence interval of standard deviation in a normal distribution

Confidence interval (CI) for a standard deviation in a normal distribution, based on pivotal quantity with a Chi-square distribution, is considered. As a measure of CI quality, the ratio of its endpoints is taken. There are given formulas for sample sizes so that this ratio does not exceed a fixed value. Both equally tailed and minimum ratio of endpoint CIs are considered.     

Analysis of Between–Household Heterogeneity in Disease Transmission from Data on Outbreak Sizes

The paper proposes a method of analysis for data on within–household disease transmission, when only outbreak sizes are available. The method assumes between–household heterogeneity of the transmission probabilities. A random effects model in a hierarchical setting is fitted using MCMC and data augmentation techniques. The procedure is illustrated on a measles dataset.     

The p-Value Requires Context,Not a Threshold

Abstract

It is widely recognized by statisticians, though not as widely by other researchers, that the p-value cannot be interpreted in isolation, but rather must be considered in the context of certain features of the design and substantive application, such as sample size and meaningful effect size. I consider the setting of the normal mean and highlight the information contained in the p-value in conjunction with the sample size and meaningful effect size. The p-value and sample size jointly yield 95% confidence bounds for the effect of interest, which can be compared to the predetermined meaningful effect size to make inferences about the true effect. I provide simple examples to demonstrate that although the p-value is calculated under the null hypothesis, and thus seemingly may be divorced from the features of the study from which it arises, its interpretation as a measure of evidence requires its contextualization within the study. This implies that any proposal for improved use of the p-value as a measure of the strength of evidence cannot simply be a change to the threshold for significance.     

When is n large enough? Looking for the right sample size to estimate proportions

The central limit theorem indicates that when the sample size goes to infinite, the sampling distribution of means tends to follow a normal distribution; it is the basis for the most usual confidence interval and sample size formulas. This study analyzes what sample size is large enough to assume that the distribution of the estimator of a proportion follows a Normal distribution. Also, we propose the use of a correction factor in sample size formulas to ensure a confidence level even when the central limit theorem does not apply for these distributions.     

Sample sizes required for binomial trials when the true response rates are estimated

Binomial trial sample size specification depends upon the values of the unknown response rate parameters, as well as upon the size and power of the resulting test. In practice, the values assumed for these parameters are based upon the results of previous or pilot trials, or upon the investigator's prior knowledge or belief. In either case, there is some uncertainty associated with these values that should be taken into account if the sample sizes are to be specified realistically. This paper describes a procedure for incorporating this uncertainty explicitly into the sample size determination on the basis of joint confidence distributions obtained from the pilot or prior information.