On some classifiers based on multivariate ranks

Non parametric approaches to classification have gained significant attention in the last two decades. In this paper, we propose a classification methodology based on the multivariate rank functions and show that it is a Bayes rule for spherically symmetric distributions with a location shift. We show that a rank-based classifier is equivalent to optimal Bayes rule under suitable conditions. We also present an affine invariant version of the classifier. To accommodate different covariance structures, we construct a classifier based on the central rank region. Asymptotic properties of these classification methods are studied. We illustrate the performance of our proposed methods in comparison to some other depth-based classifiers using simulated and real data sets.     

金融调控权的约束机制与责任分担

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Sensitive parameters

Notions such as robustness and resistance of an estimator are well known and useful. These ideas have not been fully extended to functional parameters, although it seems natural to do so. In this paper we define a sensitive parameter as one for which small changes in the underlying distribution cause large changes in the parameter value. It is demonstrated that no nontrivial, nonparametric confidence procedure can exist for such a parameter. This extends a result of Bahadur and Savage ( 1956 ). The relationship between this definition and some standard concepts in robustness theory are explored, and implications for parametric inference are studied.     

Bayes two-decision procedures for two-sample problems and rank-order data

A two-sample problem for rank-order data is formulated as a two-decision problem. Using the general Bayes solution, Bayes procedures are derived for several configurations of the set of states of nature including some for which the problem is distribution-free. It is shown that for certain prior distributions these procedures reduce to classical LMP rank tests. Some devices for selection of prior distributions are suggested. It is shown that the Bayes risk of these procedures tends to zero as sample sizes increase.     

Residual components in generalized linear models

The adequacy of a postulated generalized linear model can often be improved by transforming predictors and/or including additional explanatory variables. To assess the fit relative to a given predictor, we define its corresponding residual component. Asymptotic bias and variance of the residual component are considered, paying particular attention to the case that the presumed model is valid.     

Multiple Comparisons Controlling Expected Number of False Discoveries

In this paper, it is put forward that the task of designing a procedure for a set of multiple comparisons should be considered as a decision-making under uncertainty. Due to this motivation, for the problem of multiple comparisons, we considered another error rate to be controlled, called PFER (per-family error rate), which requests that the expected number of false rejections of a test procedure should be bounded no more than a prespecified level k. Although PFER was proposed by Tukey in 1953, there is not much studying about it so far. We first present Bonferroni procedure (single-step) and then build two step-up procedures with one having generic critical values and another using critical values in BH (Benjamini and Hochberg) type. These procedures are compared through simulations.     

A two stage procedure for selecting δ∗-optimal means in the normal model

Suppose π₁,…,π_k are k normal populations with π_i having unknown mean μ_i and unknown variance σ². The population π_i will be called δ^?-optimal (or good) if μ_i is within a specified amountδ? of the largest mean. A two stage procedure is proposed which selects a subset of the k populations and guarantees with probability at least P^? that the selected subset contains only δ?-optimal π_i ’s. In addition to screening out non-good populations the rule guarantees a high proportion of sufficiently good π_i’S will be selected.     

Biopharmaceutical applications of group sequental designs

Methods are described for calculating the properties of a general class of group sequential designs. The procedures are based on direct enumeration of a11 possible outcomes thereby giving exact results. The test regions of these designs are closed, may be one- or two-sided and may include a variable number of groups or stages. The methods described can be applied in experimental situations where the responses can be dichotomized or ranked. Specific examples which are given to illustrate the procedures include drug screening, laboratory evaluation, and clinical trials.