Some Tests for k£2 Upper Outliers in an Exponential Sample

The sequential procedure for testing up to k upper outliers proposed by Kimber (1982) for one-parameter exponential distribution is modified to a two-parameter exponential distribution. Further null distributions of some test statistics for an upper outlier-pair in a complete or censored sample from a two-parameter exponential distribution are given. Percentage points of the statistic T₁ are tabulated.     

A Space–Time Scan Statistic for Detecting Emerging Outbreaks

Summary As a major analytical method for outbreak detection, Kulldorff's space–time scan statistic (2001, Journal of the Royal Statistical Society, Series A 164, 61–72) has been implemented in many syndromic surveillance systems. Since, however, it is based on circular windows in space, it has difficulty correctly detecting actual noncircular clusters. Takahashi et al. (2008, International Journal of Health Geographics 7 , 14) proposed a flexible space–time scan statistic with the capability of detecting noncircular areas. It seems to us, however, that the detection of the most likely cluster defined in these space–time scan statistics is not the same as the detection of localized emerging disease outbreaks because the former compares the observed number of cases with the conditional expected number of cases. In this article, we propose a new space–time scan statistic which compares the observed number of cases with the unconditional expected number of cases, takes a time‐to‐time variation of Poisson mean into account, and implements an outbreak model to capture localized emerging disease outbreaks more timely and correctly. The proposed models are illustrated with data from weekly surveillance of the number of absentees in primary schools in Kitakyushu‐shi, Japan, 2006.     

Estimation of Exponential Parameters in the Presence of Outliers

In the present paper we discuss the estimation of the parameter and survival function of an exponential population. It is assumed that the sample based on which the estimation is done, contains k outliers that are also exponentially distributed with parameter, a constant multiple of that of the original distribution.     

两种体外细胞毒性检测方法的比较研究

目的比较两种常用的细胞毒性检测方法在医疗器械生物学评价中的相关性。方法分别采用MTT比色法和细胞增殖度法,在37℃条件下,将五种医疗器械／生物材料的浸提液分别与小鼠成纤维细胞（L-929）接触2天和2,4,7天,比较材料对细胞的毒性影响。结果5种不同的材料浸提液分别表现出不同程度的细胞毒性反应（0～2级）。将MTT比色法与细胞增殖度法（2天）的实验数据进行相关性分析,显示两者之间具有良好的相关性（R=0．977）。结论MTT比色法由于其检测所需的细胞量相对较少,试验步骤相对简便、检测周期短,因此具有一定的优越性,是个值得推荐的细胞毒性检测方法。     

Sample Sizes for Testing Equality of Location Parameters of Two Exponential Distributions

A table for determining minimal sample sizes n₁ = n₂ = n for testing the hypothesis of equality of location parameters a₄ and a₂ of two two-parametric exponential distributions for a first kind risk α=0,01 and 0,05 are given in such a way that the second kind risk β≦β₀ as long as |a₁–a>₂|>d.     

Exact Calculation of Permutational Distributions for Two Dependent Samples I

A simple Fortran subroutine is given for the calculation of permutational distributions. Important special cases are Fisher's randomization test, the Wilcoxon signed ranks test and the sign test. The algorithm works in polynomial time. Thus it can be used even for micro-computers within justifiable time limits.     

An Empirical Power Comparison of Three Tests of Exponentiality Under Mixture- and Outlier-Models

We present the results of an empirical power study of three prominent goodness-of-fit tests for exponentiality due to Shapiro and Wilk (1972), Durbin (1975), and Tiku (1980) by considering the mixture- and the outlier- exponential models as alternatives. This study is on similar lines as those of Dyer and Harbin (1981) and Balakrishnan (1983). We show that Tiku's test is on the whole considerably more powerful than the other two tests.     

Randomized Blocks Analysis for the Exponential Distribution

A procedure for analyzing randomized blocks experiments for uncensored exponential random variables is presented. Its small sample behavior is studied in several simulations. Sample size requirements are given.     

Exact Calculation of Permutational Distributions for Two Independent Samples

A simple Fortran Subroutine is given for the exact calculation of permutational distributions for two independent samples. Important special cases are the Fisher-Pitman randomization test, the Mann-Whitney U-test, the Mantel-Haenszel-test and the exact test for 2×k contingency tables. The algorithm needs polynomial time and is of use even for personal- or microcomputers.     

New Ranked Set Sampling for One‐Parameter Family of Distributions

Bhoj (1997c) proposed a new ranked set sampling (NRSS) procedure for a specific two‐parameter family of distributions when the sample size is even. This NRSS procedure can be applied to one‐parameter family of distributions when the sample size is even. However, this procedure cannot be used if the sample size is odd. Therefore, in this paper, we propose a modified version of the NRSS procedure which can be used for one‐parameter distributions when the sample size is odd. Simple estimator for the parameter based on proposed NRSS is derived. The relative precisions of this estimator are higher than those of other estimators which are based on other ranked set sampling procedures and the best linear unbiased estimator using all order statistics.     

Exact Tests for Comparing Two Paired Proportions with Incomplete Data

Various asymptotic test procedures have been developed previously for testing the equality of two binomial proportions with partially incomplete paired data. Test procedures that discard incomplete observations have been shown to be less powerful than those procedures that utilize all available observations. On the other hand, asymptotic test procedures that utilize all available observations may not be reliable in small‐sample problems or sparse data structures. In this article, unconditional exact test procedures are proposed for testing the equality of two paired binomial proportions with partially incomplete paired data under a random mechanism. The proposed unconditional exact test methods are illustrated with real data from a neurological study. Empirical studies are conducted to investigate the performance of these and other test procedures with respect to size and power. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Measuring Differences of Trait Distributions Between Populations

A measure of difference between populations for a trait should reflect not only the differences in the relative frequencies of the trait states but also the trait differences between the states. Common approaches to measuring differences between populations rely on distance, probability, or variance concepts. To overcome conceptual problems of these approaches, a new difference measure Δ is presented that is based on both frequency and trait differences. For two populations, Δ expresses the degree to which the frequency distribution of the trait states within one population must be transformed in order to make it match the distribution in the other population. This is done by shifting the relative frequency excesses of trait states to other trait states of deficient frequency, where shifts occur between as similar states as possible. Δ equals the minimum sum of the shifted frequencies weighted by the respective trait differences. Its bounds are functions of the difference measure d₀, which considers only differences in relative frequency. The computer program DeltaS applies an algorithm from operations research to calculate Δ. The effect of including trait differences is demonstrated by the topological differences observed between Δ‐ and d₀‐dendrograms constructed from microsatellite allele frequencies in four riparian stands of black poplar (Populus nigra), where the trait difference between two alleles equals the difference in numbers of tandem repeats. Δ is applicable to all traits for which trait differences are measurable, and it is shown to have elementary linearity properties that considerably simplify its interpretation.     

Robustness of Statistical Tests in the Two-Sample Location Problem

A simulation study was performed to compare three statistical tests with respect to their performances in the two-sample location problem for contaminated normal distributions. The three tests were: the t-test, the rank-transformed t-test, and the Wilcoxon rank-sum test. The results showed the t-test to be inferior to the other two tests.     

配对二项数据的等价性和非劣性的检验

评估两种医学诊断方法之间的等价性或非劣性在医学研究中是十分重要的．本文对此问题提出了一种适合于任意容量的检验方法．