高炮随动系统自动测试中正弦机发送频率的确定

在某型高炮随动系统测试中,正弦机的发送频率直接影响着输出信号的平滑度,从而会影响测试的精度。为了避免在正弦机运行过程中,计算耗用过多机时,在正弦机发送之前,先计算出每个位置信号、前馈信号的数值,存放于内存中。本文根据该正弦机信号的特点,分析了几种正弦机角位置信号发送频率方式的优缺点,确定了正弦机发送频率的方式。     

On Conformity Testing and the Use of two Stage Procedures

Conformity testing is a systematic examination of the extent to which an entity conforms to specified requirements. Such testing is performed in industry as well as in regulatory agencies in a variety of fields. In this paper we discuss conformity testing under measurement or sampling uncertainty. Although the situation has many analogies to statistical testing of a hypothesis concerning the unknown value of the measurand there are no generally accepted rules for handling measurement uncertainty when testing for conformity. Usually the objective of a test for conformity is to provide assurance of conformity. We therefore suggest that an appropriate statistical test for conformity should be devised such that there is only a small probability of declaring conformity when in fact the entity does not conform. An operational way of formulating this principle is to require that whenever an entity has been declared to be conforming, it should not be possible to alter that declaration, even if the entity was investigated with better (more precise) measuring instruments, or measurement procedures. Some industries and agencies designate specification limits under consideration of the measurement uncertainty. This practice is not invariant under changes of measurement procedure. We therefore suggest that conformity testing should be based upon a comparison of a confidence interval for the value of the measurand with some limiting values that have been designated without regard to the measurement uncertainty. Such a procedure is in line with the recently established practice of reporting measurement uncertainty as “an interval of values that could reasonably be attributed to the measurand”. The price to be paid for a reliable assurance of conformity is a relatively large risk that the procedure will fail to establish conformity for entities that only marginally conform. We suggest a two‐stage procedure that may improve this situation and provide a better discriminatory ability. In an example we illustrate the determination of the power function of such a two‐stage procedure.     

Correlates of Drug Testing Attitudes in a Sample of Blue Collar Workers

Using responses from 1429 workers employed in the wood products industry, we examine the relationship between drug testing (DT) attitudes and several demographic, organizational, job attitude, and job outcome variables. After controlling for age and marital status, analyses revealed moderate correlations between DT attitudes and alcohol and drug variables, DT program characteristics, organizational, and work attitude variables. DT attitudes were weakly but significantly related to absences, late work arrivals, accidents, and injuries. Implications of the findings and future research suggestions are discussed.     

Performance hypothesis testing with the Sharpe ratio: The case of hedge funds

As recent research highlights that the Sharpe ratio has a decision theoretic foundation even in the case of asymmetric or fat-tailed excess returns and thus is adequate even for the evaluation of hedge funds, this note provides the first Sharpe ratio based performance analysis of the hedge fund market. Furthermore, it addresses the important practical question whether the choice of hypothesis test used to statistically compare Sharpe ratios can influence an investor’s hedge fund selection process. Our key findings are as follows: (i) Only a small fraction of hedge funds in our large dataset can significantly outperform passive investments in corresponding hedge fund indices. (ii) Especially in the presence of autocorrelated or skewed excess returns, the traditional test of Jobson and Korkie, 1981, Memmel, 2003 tends to overstate the number of significant outperformers and thus provides potentially misleading information for investors. Decision makers are advised to use the bootstrap test of Ledoit and Wolf (2008) allowing robust and more reliable inference.     

Neoclassical versus Frontier Production Models? Testing for the Skewness of Regression Residuals*

The empirical literature on production and cost functions is divided into two strands. The neoclassical approach concentrates on model parameters, while the frontier approach decomposes the disturbance term to a symmetric noise term and a positively skewed inefficiency term. We propose a theoretical justification for the skewness of the inefficiency term, arguing that this skewness is the key testable hypothesis of the frontier approach. We propose to test the regression residuals for skewness in order to distinguish the two competing approaches. Our test builds directly upon the asymmetry of regression residuals and does not require any prior distributional assumptions.     

The Interaction between Internal Control Assessment and Substantive Testing in Audits for Fraud*

We examine the interaction between internal control assessments and substantive testing in a model of fraud detection. The purpose of our study is to examine a two‐stage model of the auditor‐manager interaction in which the auditor assesses the “likelihood” or possibility of fraud in the first stage and conducts substantive tests in the second stage. We examine the allocation of audit resources across these two distinct facets of the audit. We find that, regardless of the auditor's allocation, the probability of undetected fraud remains the same, but the allocation of some audit resources to internal control assessment may provide cost savings for the auditor.     

Memoryless Reigns of the “Sons of Heaven”

Human lifetimes have increasing failure rates; as people age (beyond early childhood) they are more likely to die. Viewing the succession of Chinese Emperors as a statistical ensemble we show that, unlike lifetimes, their reigns ceased at a constant rate for over two millennia, unaffected by elapsed time. In fact reign lengths of the “Sons of Heaven”, as the Chinese Emperors were known, followed a memoryless exponential distribution with a 10-year half-life. Becoming emperor not only influenced the duration of remaining life, but length of rule was independent of age at ascent. We propose an explanation for the observed exponentiality using asymptotic results from the theory of stationary stochastic processes.     

Test validation from a conceptual and legal perspective: Issues and trends

A little-explored issue in the psychological and legal literature involves test validation. This article discusses issues of test validation from both psychological and legal perspectives. Areas of inconsistency are noted and probable future directions are high-lighted.     

阅读测试效度浅析

阅读测试效度是以语言学习，语言教学和语言测试的研究为基础的。它包含阅读过程和阅读技巧，涉及测试目的以及所学专业知识；它包括选择相关并合适的材料，设计出合适的测试项目而又不影响被试者的阅读能力；它还要考虑题的难度和干扰项等因素。     

Diagnostics cannot have much power against general alternatives

Model diagnostics are shown to have little power unless alternative hypotheses can be narrowly defined. For example, the independence of observations cannot be tested against general forms of dependence. Thus, the basic assumptions in regression models cannot be inferred from the data. Equally, the proportionality assumption in proportional-hazards models is not testable. Specification error is a primary source of uncertainty in forecasting, and this uncertainty will be difficult to resolve without external calibration. Model-based causal inference is even more problematic.