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随机临床试验中无处理效应的检验AI 解读

We propose a test of the null hypothesis of no treatment effect in a randomized clinical trial that is based on the randomization distribution of residuals. These residuals result from regressing the response on covariates, but not treatment. In contrast to model-based score tests, this procedure maintains nominal size when the model is misspecified, and, in particular, when relevant covariates are omitted from the regression. The efficiency of the procedure is evaluated for…

指数族响应下的试验设计札记AI 解读

Some simple design problems are considered when responses have an exponential family distribution with the difference between ‘treatment’ groups in the canonical parameter being the objective of study. It is shown that normal theory conclusions apply to a possibly surprising extent. The loss from randomizing followed by subsequent stratification is the equivalent of one observation per stratum. For binary data heterogeneity has to be quite large before failure to stratify…

配对设计中以中位数进行重新随机化推断AI 解读

When a rerandomization or permutation test is applied to a matched-pairs design, the observed mean difference is typically compared with the null distribution of means that would have occurred under all possible randomizations. It is shown that rerandomizing the median instead of the mean transforms a formidable computational problem into one amenable to a hand calculator. Moreover, the robustness derived from rerandomizing the median rather than the mean is illustrated with…

残留效应与自相关误差下比较两种处理的最优交叉设计AI 解读

A model for responses in a crossover experiment that includes direct and first-order carryover treatment effects, together with an autocorrelated error term, is considered when there are two treatments. A method for generating designs that minimize the variance of the estimated treatment effects is proposed and explicit results are given for the three and four period cases. Efficiencies of some practical designs are calculated.

用于比较多种处理与对照的交叉试验设计AI 解读

We introduce a class of crossover designs with residual effects for experimental situations in which primary interest centres on the comparison of several test treatments to a control treatment rather than on all pairwise comparisons among the treatments. We shall call these designs ‘control balanced residual effects designs’. Their structure is studied in detail, some methods of their construction are given and their relative efficiencies are evaluated.

高度分层数据的修正对数秩检验AI 解读

Clinical trials often employ a stratified randomization so that treatment arms are balanced within prognostic factors. In these circumstances the use of the ordinary log rank test for comparing treatment groups with respect to survival is invalid. The stratified log rank test, although valid, loses efficiency as the number of strata increases. This paper proposes a modified log rank test that is fully efficient when there is no strata effect and is more efficient than the…

匹配观察研究中若干置换推断的敏感性分析AI 解读

In observational studies, treatments are not randomly assigned to experimental units, so that randomization tests and their associated interval estimates are not generally applicable. In an effort to compensate for the lack of randomization, treated and control units are often matched on the basis of observed covariates; however, the possibility remains of bias due to residual imbalances in unobserved covariates. A general though simple method is proposed for displaying the…

使用条件变量或因果变量的预测后果AI 解读

Forecasts based on two information sets, one of which includes the other plus additional causal variables are considered. Given a general cost function of forecast errors, it is shown that the expected cost is smaller for the information set that includes the causal variables.

用于比较多种处理与对照的交叉设计AI 解读

We introduce a class of crossover designs with residual effects for experimental situations in which primary interest centres on the comparison of several test treatments to a control treatment rather than on all pairwise comparisons among the treatments. We shall call these designs ‘control balanced residual effects designs’. Their structure is studied in detail, some methods of their construction are given and their relative efficiencies are evaluated.

存在残留效应与自相关误差时比较两种处理的最优交叉设计AI 解读

A model for responses in a crossover experiment that includes direct and first-order carryover treatment effects, together with an autocorrelated error term, is considered when there are two treatments. A method for generating designs that minimize the variance of the estimated treatment effects is proposed and explicit results are given for the three and four period cases. Efficiencies of some practical designs are calculated.

适用于高度分层数据的修正对数秩检验AI 解读

Clinical trials often employ a stratified randomization so that treatment arms are balanced within prognostic factors. In these circumstances the use of the ordinary log rank test for comparing treatment groups with respect to survival is invalid. The stratified log rank test, although valid, loses efficiency as the number of strata increases. This paper proposes a modified log rank test that is fully efficient when there is no strata effect and is more efficient than the…

匹配观察性研究中部分置换推断的敏感性分析AI 解读

In observational studies, treatments are not randomly assigned to experimental units, so that randomization tests and their associated interval estimates are not generally applicable. In an effort to compensate for the lack of randomization, treated and control units are often matched on the basis of observed covariates; however, the possibility remains of bias due to residual imbalances in unobserved covariates. A general though simple method is proposed for displaying the…

统计学与因果推断AI 解读

Problems involving causal inference have dogged at the heels of statistics since its earliest days. Correlation does not imply causation, and yet causal conclusions drawn from a carefully designed experiment are often valid. What can a statistical model say about causation? This question is addressed by using a particular model for causal inference (Holland and Rubin 1983; Rubin 1974) to critique the discussions of other writers on causation and causal inference. These…

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实验面板数据中的样本流失与劳动供给反应AI 解读

Sample attrition is a potentially serious problem for analysis of panel data, particularly experimental panel data. In this article, a variety of estimation procedures are used to assess the importance of attrition bias in labor supply response to the Seattle and Denver Income Maintenance Experiments (SIME/DIME). Data from Social Security Administration earnings records and the SIME/DIME public use file are used to test various hypotheses concerning attrition bias. The study…

随机删失下与V统计量相关的经验过程及一类估计量AI 解读

A class of empirical processes associated with $V$-statistics ($V$-empirical process) under random censoring, and a class of nonparametric estimators based on the corresponding quantile process are defined. The $V$-empirical process is the censored data analogue of the $U$-empirical process considered by Silverman (1976, 1983). The class of estimators is the analogue of the class of generalized $L$-statistics introduced by Serfling (1984) and it includes the results of…

马来西亚儿童健康、母乳喂养与存活：随机效应Logit方法AI 解读

This study examines the possibility that estimation of the effect of breast-feeding on infant survival is affected by selection bias, in that children who are healthier at birth may be more likely to be breast-fed. Data are from the 1976 Malaysian Family Life Survey. "Ordinary logit models for breast-feeding and survival are estimated, and the results suggest that selection is indeed present. For example, children of higher birth weight appear to be more likely to be…

用于处理与对照比较的渐近最优平衡处理不完全区组设计子类AI 解读

Incomplete block designs for estimation of treatment-control differences are studied. A class of designs for this purpose, called balanced treatment incomplete block designs, has recently been proposed and studied by several authors. Here, a relatively small subclass of these designs is shown to contain the asymptotically optimal design under the criterion of minimizing the length of simultaneous confidence intervals for treatment-control differences. These results can be…

结合显著性预检验的最优样本设计AI 解读

A common problem faced in social experiments is that of designing a sampling strategy before it is known whether various control groups can be pooled. The classical sample choice is between a large supposedly unpoolable sample or a smaller supposedly poolable sample. This article suggests a compromise strategy between these two extremes based on preliminary tests of significance that allow one to embed judgments about the likelihood of pooling into a classical sample design…

临床试验中受限随机化规则下的多处理比较AI 解读

In the course of conducting a clinical trial to compare $K (\geq 2)$ treatments, it is often desirable to balance the trial with respect to the assignments of patients to treatments. On the other hand, some form of randomization of treatment assignments is essential for reducing experimental bias. In this article, the large-sample approximation to the null distribution of $K$-sample randomization tests generated from a broad class of restricted randomization rules is…

具有调整正交性的行列设计中行间与列间信息的恢复AI 解读

SUMMARY The analysis of row-column designs which satisfy the property of adjusted orthogonality is considered. For such designs a series of results are derived which relate the information matrix, its inverse, the estimator of the treatment effects and the adjusted treatment sum of squares to those of its component designs. It is also shown that estimators of the stratum variances required for the recovery of information from between rows and between columns can be obtained…

协方差分析中的随机化AI 解读

When examining any linear contrast of adjusted treatment means in the analysis of covariance it is shown that balancing on the covariates is desirable in that it minimizes the model variance of the treatment contrast averaged over the randomization distribution. Approximate balancing, through truncation of the randomization distri bution, is examined empirically. It is shown empirically that robustness of the test statistic can be achieved through truncated randomization.…

用于处理与对照比较的渐近最优平衡处理不完全区组设计子类AI 解读

Incomplete block designs for estimation of treatment-control differences are studied. A class of designs for this purpose, called balanced treatment incomplete block designs, has recently been proposed and studied by several authors. Here, a relatively small subclass of these designs is shown to contain the asymptotically optimal design under the criterion of minimizing the length of simultaneous confidence intervals for treatment-control differences. These results can be…

最小二乘与误差变量回归的比较：聚焦随机化协方差分析AI 解读

In an errors-in-variables regression model, the least squares estimate is generally inconsistent for the complete regression parameter but can be consistent for certain linear combinations of this parameter. We explore the conjecture that, when the least squares estimate is consistent for a linear combination of the regression parameter, it will be preferred to an errors-in-variables estimate, at least asymptotically. The conjecture is false, in general, but it is true for…