非参数统计的SAS计算

ＳＡＳ软件ＳＴＡＴ模块的ＮＰＡＲ1ＷＡＹ过程,专门用于非参数分析,其他过程也可作此分析。最近几本有关ＳＡＳ的统计学教材〔1,2〕介绍了一些程序,但对有些资料,如整理为频数表的等级资料,ｋ个相关样本的比较资料等,作非参数分析没有给出程序。为此,本文重点针对这类资料编写了ＳＡＳ程序,并根据资料的类型,给出了非参数统计的ＳＡＳ实现方案。一、资料分布的检验大多数参数统计需要假设资料服从正态分布,如果资料不满足这一条件,统计分析最好采用非参数法。在ＳＴＡＴ模块的ＵＮＩＶＡＲＩＡＴＥ过程中加入ＮＯＲＭＡＬ选项,可作正态性检…     

非参数统计分析

一般应用统计方法进行显著性检验时，常用的样本为随机样本皆来自已知总体的分布函数类型，从而由样本的结果对总体参数做检验即参数检验方法。在实际研究中对总体分布的假定有时与估计有偏离或未知总体分布，在此情况下，对总体某些假设进行检验时应用非参数检验。 非参数检验又称分布自由检验，主要是不受总体分布的限制。对某些资料若只用严重程度、优劣等级、先后次序等记录时也可处理，方法简便易于理解与掌握。当然如可用参数估计或参数检验的资料，而用非参数检验则会损失一定信息，检验效率比参数检验要低。因而使用非参数检验方法…     

组群趋势的非参数统计方法

若有ｋ组计量数据符合条件，可作方差分析以回答是否ｋ个总体均数相等，否则，需用非参数的ＫｒｕｓｋａｌＷａｌｓ方法分析ｋ个总体分布位置是否相同。对于随机区组设计资料，用方差分析或Ｆｒｉｄｍａｎ方法也同样只能回答上述两个问题。倘若ｋ个组的分组是有序的，如...     

袖珍计算器程序法计算分组数据的统计参数

大样本分组数据统计参数的计算主要为算术平均值和标准差、几何均数和几何标准差。现行医学统计工作中一般多采用简捷计算方法。简捷算法为一手算列表计算方法,其计算中间过程甚多、速度慢,且易出差错。对于多个大样本的分组数据计算,就更显得该计算法需耗大量的人力和时间。     

非参数统计分析(续)

2　Ｒｉｄｉｔ分析法Ｒｉｄｉｔ是参照单位 (Ｒｅｌａｔｉｖｅｔｏａｎｉｄｅｎｔｉｆｉｅｄｄｉｓｔｒｉｂｕｔｉｏｎｕｎｉｔ)的意思。分析法是 195 6年Ｂｒａｓｓ首先提出的一种分析等级资料的统计方法。主要思想是在各比较组中找出一个统一的参照组做为标准。先假定以此标准组作为标准总体 ,并求出该总体等级的平均值 Ｒ标准 =0 .5 (可证明此值的计算结果总为 0 .5 ,本文略 )。另设对比组为来自该标准总体的随机样本 ,该对比组的 Ｒ值的可信区间包括 0 .5的概率为 (1 α) ,如不包括 0 .5则可根据检验水准α拒绝假设 ,而认为对比组与标…     

制定多元医学参考范围的非参数统计方法

目前,虽然已经有好几种统计方法可用于制定多元医学参考范围,如多元正态容许区间法、多元回归法和多维标度法等,但由于这些方法计算复杂,结果表达不够直观,或对资料有较严的要求(如多元正态分布),影响了多元医学参考范围的普及和应用。为了克服上述方法的缺点,本文提出了制定多元医学参考范围的非参数方法。该方法是制定一元医学参考范围的百分位数法在多元情况下的推广,具有非参数统计方法的种种优点,如对资料的分布没有任何要求,道理浅显,计算简便,结果表达直观等,是医学研究工作者制定多元医学参考范围较理想的统计方法。     

统计参数图在Bold—fMRI研究中的应用评价

目的：探讨统计参数图在Bold—fMRI研究中的应用价值。方法：对87例被试者的脑功能数据用统计参数图软件包离线处理，经过一系列的预处理和统计分析，得到脑激活统计参数图．研究激活区与解剖功能区的对应关系．并生成各种量化分析数据进行统计学处理。结果：正常对照组被试数据经统计参数图后处理结果符合诊断要求的百分率大于异常被试组。结论：统计参数图内置多项预处理步骤．可较有效地排除或减弱被试者的头动、心跳、呼吸及MRI设备系统噪声等干扰因素造成的伪影／影响．有效的预处理在肢体运动功能异常者的Bold—fMRI数据处理中起了至关重要的作用，是确保Bold—fMRI激活结果灵敏性和可靠性的关键手段。     

非参数bootstrap方法在验证统计模型参数估计值稳定性方面的应用

考察统计模型参数估计值的稳定性，最好的方法是增大样本含量后用原方法重新拟合模型，若得到的参数估计值与原参数估计值接近，则可认为原参数估计值的稳定性较好。但实际工作中由于时间、人力、物力和财力的限制，增大样本含量重新搜集资料，实施起来非常困难。另一种常用方法是将原样本分成样本含量相等或不相等的两个或两个以上的亚样本。     

老年缺铁性贫血患者血清铁参数和血小板参数检测结果分析

缺铁性贫血是一种全球范围内的常见病。在任何年龄和各种经济状况的人群中均有发病。但多见婴儿、儿童、妇女及贫穷人群。据世界卫生组织(WHO)2002年资料显示:目前全世界铁缺乏人数可达20亿。占世界人口的30%。我国孕妇、儿童、青少年和育龄妇女缺铁性贫血患病率分别为20%、35.1%、30%和15%,远远高于西方发达国家。近年来,老年人群缺铁性贫血明显升高,大约5%～7%的60岁以上老年     

无金标准诊断实验条件下贝叶斯先验参数的确定方法及SAS实现

目的探讨无金标准诊断实验条件下,贝叶斯先验参数的确定方法,并比较不同方法的应用条件。方法根据贝叶斯共轭先验分布原理,对二项分布的共轭贝塔分布中的α、β两个先验参数的确定方法进行分析比较,编写SAS程序确定先验参数。结果在共轭先验分布的条件下,先验矩、分位数、众数与分位数三种方法确定的先验分布参数结果一致。结论在实际工作中,应根据已知条件和具体情况决定采用何种方法计算先验分布参数。     

13C尿素呼气试验质谱仪的重复性及影响因素

目的:13C质谱法尿素呼气试验是对幽门螺旋杆菌检测的“金标准”,检验该方法的重复性并找出其影响因素.方法:使用双通道进样气体核素比值质谱仪,以13CO2超量δ值为结果,对无感染幽门螺旋杆菌的受检者所吹的气样,做Friedman按秩的双向方差分析.感染幽门螺旋杆菌的受检者在服用13C标记的尿素后所吹的气样,18根试管在放置2～10h后重复测量4次,做配对t检验.结果:阴性试管测试:复测所得δ值(±SD)为-24.54±0.86,-24.37±0.81,平均秩分别为1.16,1.84；P＜0.001,复测δ值升高.5组δ值平均秩分别为1.77,1.77,2.98,3.63,4.86;P＜0.001,5次测量结果逐渐升高.阳性试管测试:18对δ值平均秩分别为1.28,1.89,2.89,4.06,4.89,P＜0.001.以上检验结果差异均有统计学意义.结论:13C质谱法测量幽门螺旋杆菌尿素呼气试验,其试管不能过多复测.长时间放置的试管或机器温度的变化会对δ值有影响,但变化较小.     

Detecting case-control expression quantitative trait loci using locally most powerful or maximin robust rank tests

In testing genome-wide gene expression quantitative trait loci, efficiency robust statistical methods and their computational convenience are most relevant. For this purpose, we propose to use a modified locally most powerful rank test for the analysis of case-control expression data. This modified rank test statistic is computationally simple, robust for non-normally distributed expression data, and asymptotically locally most powerful. It depends on the specification of a location distribution form for data but is not sensitive to misspecifications. When such a location distribution form cannot be specified, we apply Gastwirth's maximin efficiency robust rank test to gene expression data to maximize the worst Pitman asymptotic relative efficiency among a family of location distributions. We conduct simulation studies to assess their performance and use an application to real data for illustration.     

Power and sample size calculations for the Wilcoxon–Mann–Whitney test in the presence of death‐censored observations

We consider a clinical trial of a potentially lethal disease in which patients are randomly assigned to two treatment groups and are followed for a fixed period of time; a continuous endpoint is measured at the end of follow‐up. For some patients; however, death (or severe disease progression) may preclude measurement of the endpoint. A statistical analysis that includes only patients with endpoint measurements may be biased. An alternative analysis includes all randomized patients, with rank scores assigned to the patients who are available for the endpoint measurement on the basis of the magnitude of their responses and with ‘worst‐rank’ scores assigned to those patients whose death precluded the measurement of the continuous endpoint. The worst‐rank scores are worse than all observed rank scores. The treatment effect is then evaluated using the Wilcoxon–Mann–Whitney test. In this paper, we derive closed‐form formulae for the power and sample size of the Wilcoxon–Mann–Whitney test when missing measurements of the continuous endpoints because of death are replaced by worst‐rank scores. We distinguish two approaches for assigning the worst‐rank scores. In the tied worst‐rank approach, all deaths are weighted equally, and the worst‐rank scores are set to a single value that is worse than all measured responses. In the untied worst‐rank approach, the worst‐rank scores further rank patients according to their time of death, so that an earlier death is considered worse than a later death, which in turn is worse than all measured responses. In addition, we propose four methods for the implementation of the sample size formulae for a trial with expected early death. We conduct Monte Carlo simulation studies to evaluate the accuracy of our power and sample size formulae and to compare the four sample size estimation methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Evaluating guidelines for "selection and training of staff for odor analysis"--a 7-year longitudinal study

During a 7 years longitudinal study on a representative group the guideline "selection and schooling of personal for odour analysis" was reexamined. It could be shown that the selection in two steps is well suited to recognize anosmia and hyposmia, respectively and that normal osmia is well to be characterized by smell scores of 30-42. A statistical significant training effect could be shown with the qualitative test for training of the odour memory as well as the articulation in describing of smell impressions. The result of the rank order test demonstrate the practicable subdivision of the odour intensity into 5 degrees.     

Power and sample size calculation for log‐rank test with a time lag in treatment effect

The log‐rank test is the most powerful non‐parametric test for detecting a proportional hazards alternative and thus is the most commonly used testing procedure for comparing time‐to‐event distributions between different treatments in clinical trials. When the log‐rank test is used for the primary data analysis, the sample size calculation should also be based on the test to ensure the desired power for the study. In some clinical trials, the treatment effect may not manifest itself right after patients receive the treatment. Therefore, the proportional hazards assumption may not hold. Furthermore, patients may discontinue the study treatment prematurely and thus may have diluted treatment effect after treatment discontinuation. If a patient's treatment termination time is independent of his/her time‐to‐event of interest, the termination time can be treated as a censoring time in the final data analysis. Alternatively, we may keep collecting time‐to‐event data until study termination from those patients who discontinued the treatment and conduct an intent‐to‐treat analysis by including them in the original treatment groups. We derive formulas necessary to calculate the asymptotic power of the log‐rank test under this non‐proportional hazards alternative for the two data analysis strategies. Simulation studies indicate that the formulas provide accurate power for a variety of trial settings. A clinical trial example is used to illustrate the application of the proposed methods. Copyright © 2009 John Wiley & Sons, Ltd.     

指标秩次替代原始指标值聚类分析的应用研究

目的：探讨用指标秩次替代原始指标值进行聚类分析的可行性，为卫生监测工作的分类管理提供理论依据。方法：分别对实例标化后的指标秩次和原始指标值进行聚类分析，比较聚类结果的一致性。结果：实例中对指标秩次的聚类分析结果与相对应的原始指标值的聚类分析结果基本一致。结论：用指标秩次进行聚类分析可使数据化繁为简，其结果能反映对原始指标值的聚类分析，在卫生监测工作的分类管理中较具参考价值。     

Comparisons of two-part models with competitors

Two-part models arise when there is a clump of 0 observations in a distribution of continuous non-negative responses. Several methods for comparing two such distributions are available. These include the straightforward application of the z-test (or t-test), the Wilcoxon-Mann-Whitney rank sum test, the Kolmogorov-Smirnov test, and three tests that use a 2 degree of freedom chi(2) test based on the sum of the test for equality of proportions and a conditional chi(2) test for the continuous responses. This conditional test may be the z-test, the rank sum test, or the chi(2) corresponding to the Kolmogorov-Smirnov test. This study compares the size and power of several of these methods. All tests have the appropriate distribution under the null hypothesis if the distribution of the continuous part has finite moments. If it does not, the z-test has no power to detect any alternatives. It is found that the 2 d.f. tests are superior to the others when the larger proportion of 0 values corresponds to the population with the larger mean. If the reverse holds, the difference in the proportion of zeros reinforces the difference in means and some single-part models (the rank sum or Kolmogorov-Smirnov) do best. In those cases, the two-part models are not far behind, although statistically significantly poorer with respect to power. Published in 2001 by John Wiley & Sons, Ltd.     

New simple tests for age-at-onset anticipation: application to panic disorder

Recently, testing for anticipation has received renewed interest. It is well known that standard statistical methods are inappropriate for this purpose due to problems of sampling bias. Few statistical tests have been proposed for comparing mean age of onset in affected parents with mean age of onset in affected children. All of them are difficult to compute and lack software to perform the tests. In this report, we formulate the problem in terms of symmetry tests. We propose a simple generalized paired t-test and a Wilcoxon signed rank test to adjust for the bias caused by the right truncation of both the parent's and child's ages at onset. We also extend the generalized paired t-test to a random effects model that enables analysis of correlated data from nuclear families, and could be further extended to larger family structures. We illustrate the approaches with an example of panic disorder.     

Immune response to flour and dust mites in a United Kingdom bakery.

In a study of 279 United Kingdom bakery workers a high prevalence of immunological response to storage mites was found. To determine whether this was the consequence of exposure to storage mites in bakery work, a population of salt packing workers was examined as a comparison group not at occupational risk of exposure to storage mites. Forty two per cent of both groups were atopic (had a positive skin prick response greater than negative controls to D pteronyssinus, grass pollen, or cat fur by 2 mm or more) and 33% had an immediate skin prick test response to at least one of four storage mites (L destructor, G domesticus, T putrescentiae, A Siro). A higher percentage of the salt packing workers than the bakery workers had a positive radioallergosorbent test (RAST) (greater than or equal to 0.35 PRU) to D pteronyssinus and to the four storage mites. Logistic regression analysis identified atopy as the most significant variable for a positive skin test and RAST response to storage mites in both groups of workers. RAST inhibition was used to analyse extracted area and personal air samples. Analysis of static area samples for aeroallergen showed immunological identity with flour but L destructor was found in only one of seven exposed filters. The concentration of airborne flour was related to exposure rank of perceived dustiness and gravimetric measurement of total dust. Nineteen out of 32 filters from workers in jobs with higher dust exposure (rank >/=6) had a level of > 10 microgram/m(3) flour whereas this concentrations was exceeded in only one of 23 filters from workers in low dust exposure (< rank 6). It is concluded that storage mites are not of special significance in allergic responses in bakery workers. The development of immunological (and airway) responsiveness to inhaled flour dust is increased in those exposed to higher concentrations of airborne allergen, which appears to be predominantly flour and not storage mites.     

Diagnostics for assumptions in moderate to large simple clinical trials: do they really help?

In this article, primarily we look at a case study, where prior to conducting the major efficacy analysis, one performs a diagnostic test for assumptions, and acts upon the result if the diagnostic test rejects the assumptions. Specifically, we show by an example that a hybrid approach of using a diagnostic test for equality of variance in a two-sample t-test situation can adversely affect, rather than protect, the operating characteristics of the study. If this kind of hybrid approach fails in such a simple setting, analysts should be very cautious about using hybrid approaches in more complex analyses of efficacy. Secondarily, we present rationale as to why the classical tests (or slightly modified versions) can be viewed as asymptotically non-parametric, and can actually be more robust against failure of assumptions than rank tests. Readers are cautioned that this illustration is limited to efficacy analysis, and is not meant as a criticism of other analyses, such as modelling or exploratory ones.