Missing Data and Multiple Imputation in the Context of Multivariate Analysis of Variance

Multivariate analysis of variance (MANOVA) is widely used in educational research to compare means on multiple dependent variables across groups. Researchers faced with the problem of missing data often use multiple imputation of values in place of the missing observations. This study compares the performance of 2 methods for combining p values in the context of a MANOVA, with the typical default for dealing with missing data: listwise deletion. When data are missing at random, the new methods maintained the nominal Type I error rate and had power comparable to the complete data condition. When 40% of the data were missing completely at random, the Type I error rates for the new methods were inflated, but not for lower percents.     

Biased sampling activity: an investigation to promote discussion

The statistical concept of sampling is often given little direct attention, typically reduced to the mantra “take a random sample”. This low resource and adaptable activity demonstrates sampling and explores issues that arise due to biased sampling.     

大数据环境下抽样调查课程的教学改革与实践

抽样调查是统计学专业的一门专业必修课,是一门兼具理论性与应用性的课程。大数据是随着社交网络、物联网、云计算等的兴起而产生的一个新兴产业,大数据时代数据的获取方式和数据规模及其复杂程度发生了根本的变化,大数据在数据来源上对传统的抽样调查方法产生了冲击。本文主要探讨大数据环境下抽样调查课程的教学改革与实践。     

一种基于采样的并行电力负荷数据流划分方法

为了解决电力工业中并行数据流范围聚集的连续查询问题,提出一种新颖的数据流划分方法.首先构造了一个适用于数据流处理的扩展蓄水池抽样算法,根据流值变化率引入跳跃因子反应负荷数据的变化情况,实现数据流的自适应并行采样.然后为了实现数据流量的平均划分,基于近似技术提出2种适应不同情况的生成等深柱状图的算法:增量更新的启发式方法和周期性更新的快捷方法,从而在采样的基础上生成近似划分向量.通过在实际数据集上对算法性能测试,证明文中提出的数据流划分方法高效实用,适合于高速时变数据流的处理.     

空气总氟的测定方法

本文通过洛阳市环境氟水平调查的204次奉样,对空气总氟的测定技术进行了探讨,提出了适合基层的秉样和分析方法,结果表明:标准曲线法具有方便、快速,适合于大批样品的特点,对9种浓度进行了36次AQC实验,其平均标准偏差0.74—0.89,回收率100～104％;当采样体积10m~3时,最低检出浓度8×10-3mg/m~3。     

时间取样观察法的优缺点及其适用性问题

关于社会行为发展的研究大都采用时间取样观察法。该方法用于估计实际行为出现的次数、频率和持续时间以及测量群体或个体的差异。但许多研究表明，时间取样观察法存在着一些不足与局限，如时间取样法不能精确地估计行为的频率和持续时间；对个体或群体差异的测量不准确等。而且，有些研究是不适合用时间取样观察法的。因此如果所取样的行为持续时间很短的话，研究可以选择更为有效的观察法，如事件取样观察法、顺序取样法等来进行研究。     

河北省高校毕业生就业情况抽样调查问卷分析——以2012届高职毕业生为例

课题组成员在科学设计抽样．严格实施调查的基础上,取得了“我省高校毕业生就业情况抽样调查——以2012届高职毕业生为例”的第一手资料,重点分析了毕业生的择业观念、就业形势判读、知识与岗位匹配与能力胜任、就业中面临的困难和影响因素以及毕业生对学校就业支持的看法等内容,并提出了相应的解决建议。     

5ayes统计中两种抽样法的比较分析

拒绝性抽样法和重要性抽样法是贝叶斯统计中两种重要的产生模拟样本的方法．两种方法之间存在一些关联,拒绝性抽样法在做一些形式上的转变后可以看作一种特殊的重要性抽样法．此外,如果将拒绝性抽样法中的包络函数作为重要性抽样法中的提议密度函数,这样新形成的抽样法会比原本的拒绝性抽样法更为有效．     

基于STM32和增量PID的旋转倒立摆的设计

旋转倒立摆系统应用广泛,但是传统设计中存在成本较高、功耗较大等问题.针对该难题,提出利用32位低功耗嵌入式芯片STM32作为主控制器、以增量PID和惯性起摆为控制算法的解决思路.通过连续多次采样角度传感器WDX35D,STM32将获取的数值进行增量PID计算并产生PWM信号,使BTS7960能够快速、平滑地驱动伺服电机,实现摆杆进入稳定的倒立状态.实践表明,该倒立摆稳定、可靠、运行平滑、抗干扰能力强,具有低成本、低功耗等优点.     

Qualifying teacher work: everyday work as basis for the autonomy of the teaching profession

Teachers’ work in tuition‐free (non‐classroom) time was investigated to see to what degree teachers do work that could be considered as qualifying for the status of professional autonomy. The question arises in Sweden and elsewhere as both teachers and the state actively, and in tandem, strive to professionalise the work of the teacher. Abbott’s work on the division of expert labour is taken as a point of departure. Based on data collected by an organisation sampling method, the article describes what teachers do in their tuition‐free time. The study data consist of 1166 reports from 59 Swedish teachers’ daily work situations in school years 1–12. Qualifying teacher work is related to teachers’ ways of handling divergent cases, discretionary work and problem solving. Situations where teachers can use specific professional knowledge are described. One of the main findings is that in 22.2% of the situations studied, such professional knowledge can be applied. This corresponds to at least 7.5 hours of the Swedish teachers’ weekly working hours; with the reservation that 10 hours of teachers’ weekly 45 hours working time is not examined. This time corresponds roughly with the non‐regulated working time, that is, time when the teachers do not have to be at school.