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1.
标准差是心理实验中数据处理常见的重要统计量。常见的四个标准差有着严格的定义和特定的使用条件,它们之间有着特殊的转化关系。据此可简化假设检验过程,提高统计推断的准确性． 相似文献
2.
利用科学计算器直接计算出总标准差和总方差以及处理标准差和处理方差,然后用方差乘以自由度得到二者的平方和,再根据平方和公式计算出误差的平方和及方差。该方法在计算程序上比传统方法更简便,可用于统计计算和教学。 相似文献
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Lisbeth K. Cordani 《Teaching Statistics》2013,35(3):123-126
This article explores an example in finances in order to motivate the random variable learning to the very beginners in statistics. In addition, it offers a relationship between standard deviation and range in a very specific situation. 相似文献
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One common phenomenon in Angoff standard setting is that panelists regress their ratings in toward the middle of the probability scale. This study describes two indices based on taking ratios of standard deviations that can be utilized with a scatterplot of item ratings versus expected probabilities of success to identify whether ratings are regressed in toward the middle of the probability scale. Results from a simulation study show that the standard deviation ratio indices can successfully detect ratings for hard and easy items that are regressed in toward the middle of the probability scale in Angoff standard‐setting data, where previously proposed indices often do not work as well to detect these effects. Results from a real data set show that, while virtually all raters improve from Round 1 to Round 2 as measured by previously developed indices, the standard deviation ratios in conjunction with a scatterplot of item ratings versus expected probabilities of success can identify individuals who may still be regressing their ratings in toward the middle of the probability scale even after receiving feedback. The authors suggest using the scatterplot along with the standard deviation ratio indices and other statistics for measuring the quality of Angoff standard‐setting data. 相似文献
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ABSTRACT: This paper discusses the reliance of numerical analysis on the concept of the standard deviation, and its close relative the variance. It suggests that the original reasons why the standard deviation concept has permeated traditional statistics are no longer clearly valid, if they ever were. The absolute mean deviation, it is argued here, has many advantages over the standard deviation. It is more efficient as an estimate of a population parameter in the real-life situation where the data contain tiny errors, or do not form a completely perfect normal distribution. It is easier to use, and more tolerant of extreme values, in the majority of real-life situations where population parameters are not required. It is easier for new researchers to learn about and understand, and also closely linked to a number of arithmetic techniques already used in the sociology of education and elsewhere. We could continue to use the standard deviation instead, as we do presently, because so much of the rest of traditional statistics is based upon it (effect sizes, and the F-test, for example). However, we should weigh the convenience of this solution for some against the possibility of creating a much simpler and more widespread form of numeric analysis for many. 相似文献
6.
ROBERT F. McMORRIS 《Journal of Educational Measurement》1972,9(2):113-122
What is the extent of error likely with each of several approximations for the standard deviation, internal consistency reliability, and the standard error of measurement? To help answer this question, approximations were compared with exact statistics obtained on 85 different classroom tests constructed and administered by professors in a variety of fields; means and standard deviations of the resulting differences supported the use of approximations in practical situations. Results of this analysis (1) suggest a greater number of alternative formulas that might be employed, and (2) provide additional information concerning the accuracy of approximations with non-normal distributions. 相似文献
7.
We explain how to simulate both univariate and bivariate raw data sets having specified values for common summary statistics. The first example illustrates how to ‘construct’ a data set having prescribed values for the mean and the standard deviation – for a one‐sample t test with a specified outcome. The second shows how to create a bivariate data set with a specified correlation coefficient. 相似文献
8.
An empirical comparison of the accuracy of item sampling and examinee sampling in estimating norm statistics. Item samples were composed of 3, 6, or 12 items selected from a total test of 50 multiple-choice vocabulary questions. Overall, the study findings provided empirical evidence that item sampling is approximately as effective as examinee sampling for estimating the population mean and standard deviation. Contradictory trends occurred for lower ability and higher ability student populations in accuracy of estimated means and standard deviations when the number of items administered increased from 3 to 6 to 12. The findings from this study indicate that the variation of sequences of items occurring in item sampling need not have a significant affect on test performance. 相似文献
9.
针对含自由曲面及标准解析曲面零件加工精度的高精度检测,本文提出一种形状公差评定的新方法——面向CAD模型的曲面形状误差检验。它实现了各种标准解析曲面和自由曲面形状的高精度检测,采用表达式精确地表示各种标准解析曲面和自由曲面;利用数据库技术研究CMM测量点云和CAD模型的最佳匹配算法;比较测量点云和CAD模型的法向偏移量即曲面形状误差,且用图形直观地显示出来。最后进行计算机仿真实验,实例验证算法可行性。 相似文献
10.
采用测试法、文献资料法和数理统计法,对宁德范学院大学生体质健康标准测试数据进行分析与研究．结果表明：学生的体质健康状况不容乐观,身体形态发育水平中较轻体重人数占相当比例,影响学生身体机能和素质发展,肺活水平较差,心血管和呼吸系统功能及肌肉耐力呈下降趋势,各项素质能力有待提高．为此,学校应更新教学理念,深化体育教学改革和贯彻落实《国家学生体质健康标准》,提商学生的体质健康． 相似文献
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将社会主义核心价值体系这一理论创新成果社会化、大众化,真正化作广大干部群众的价值追求和行为准则,是一个重大的现实课题。调查显示,当前干部群众对社会主义核心价值体系认知度高、认同感强,但仍有部分人存在认识偏差,需要通过卓有成效的教育引导、舆论宣传、文化熏陶、实践养成、制度保障等,使社会主义核心价值体系内化为人们的价值观念,外化为人们的自觉行动。 相似文献
13.
大学排行榜层出不穷,良莠不齐,一所高校在不同排行榜中位次不尽相同,有时差异巨大。本文以QS、THE、USNews、ARWU 四个国内比较普遍关注的世界大学排行榜2016 年度发布的排名数据为基础,计算同一高校在四个排行榜中排名结果的标准差值,分析高校在多个排行中排名结果的一致性,并对排名位次和排名结果进行了关联分析。 相似文献
14.
The Angoff method requires experts to view every item on the test and make a probability judgment. This can be time consuming when there are large numbers of items on the test. In this study, a G-theory framework was used to determine if a subset of items can be used to make generalizable cut-score recommendations. Angoff ratings (i.e., probability judgments) from previously conducted standard setting studies were used first in a re-sampling study, followed by D-studies. For the re-sampling study, proportionally stratified subsets of items were extracted under various sampling and test-length conditions. The mean cut score, variance components, expected standard error (SE) around the mean cut score, and root-mean-squared deviation (RMSD) across 1,000 replications were estimated at each study condition. The SE and the RMSD decreased as the number of items increased, but this reduction tapered off after approximately 45 items. Subsequently, D-studies were performed on the same datasets. The expected SE was computed at various test lengths. Results from both studies are consistent with previous research indicating that between 40–50 items are sufficient to make generalizable cut score recommendations. 相似文献
15.
Michael J. Weiss Howard S. Bloom Natalya Verbitsky-Savitz Himani Gupta Alma E. Vigil Daniel N. Cullinan 《Journal of research on educational effectiveness》2017,10(4):843-876
Multisite trials, in which individuals are randomly assigned to alternative treatment arms within sites, offer an excellent opportunity to estimate the cross-site average effect of treatment assignment (intent to treat or ITT) and the amount by which this impact varies across sites. Although both of these statistics are substantively and methodologically important, only the first has been well studied. To help fill this information gap, we estimate the cross-site standard deviation of ITT effects for a broad range of education and workforce development interventions using data from 16 large multisite randomized controlled trials. We use these findings to explore hypotheses about factors that predict the magnitude of cross-site impact variation, and we consider the implications of this variation for the statistical precision of multisite trials. 相似文献
16.
周崇谦 《张家口职业技术学院学报》2000,(4)
“替”有二二替和二四替两种,“失替”是识别词的拗句的唯一标准。对422个词牌中每句平仄格律的统计和分析说明:律句对词的平仄句式的影响表现在,词的句子99％都是律句,将近1％的是拗句。 相似文献
17.
刘小辉 《泉州师范学院学报》2008,26(6):5-8
随机过程模型能较好描述截面抗力问题,但参数的增加会使问题的复杂程度进一步扩大,而阶梯过程描述结构荷载可较好解决上述问题．为更好对阶梯过程的模型进行可靠性分析,文章把荷载取值出现跳跃时间间隔假设为随机变量,利用积分方程给出了荷载最大值的分布函数Fη（t,x）和密度函数fη（t,x）,进一步得到η的均值和标准差的近似求法． 相似文献
18.
The novel method of improving the quality metric of protein microarray image presented in this paper reduces impulse noise by using an adaptive median filter that employs the switching scheme based on local statistics characters; and achieves the impulse detection by using the difference between the standard deviation of the pixels within the filter window and the current pixel of concern. It also uses a top-hat filter to correct the background variation. In order to decrease time consumption, the top-hat filter core is cross structure. The experimental results showed that, for a protein microarray image contaminated by impulse noise and with slow background variation, the new method can significantly increase the signal-to-noise ratio, correct the trends in the background, and enhance the flatness of the background and the consistency of the signal intensity. 相似文献
19.
The novel method of improving the quality metric of protein microarray image presented in this paper reduces impulse noise by using an adaptive median filter that employs the switching scheme based on local statistics characters; and achieves the impulse detection by using the difference between the standard deviation of the pixels within the filter window and the current pixel of concern. It also uses a top-hat filter to correct the background variation. In order to decrease time consumption, the top-hat filter core is cross structure. The experimental results showed that, for a protein microarray image contaminated by impulse noise and with slow background variation, the new method can significantly increase the signal-to-noise ratio, correct the trends in the background, and enhance the flatness of the background and the consistency of the signal intensity. 相似文献
20.
就业率的计算依赖于两个重要指标,一是劳动力资源总量,二是就业人口数。以人口普查资料为基准计算劳动力资源总量比较准确,而由城镇单位劳动统计、工商行政管理对私营企业和个体工商户的行政登记,以及多村就业人员统计三者组成的“三合一”劳动统计得到的就业人口数不准确,存在很多问题,造成就业率统计偏差。 相似文献