Blocked-Error-R 2: A Conceptually Improved Definition of the Proportion of Explained Variance in Models Containing Loops or Correlated Residuals

Bentler and Raykov (2000, Journal of Applied Psychology 85: 125–131), and Jöreskog (1999a, http://www.ssicentral.com/lisrel/column3.htm, 1999b http://www.ssicentral. com/lisrel/column5.htm) proposed procedures for calculating R ² for dependent variables involved in loops or possessing correlated errors. This article demonstrates that Bentler and Raykov’s procedure can not be routinely interpreted as a “proportion” of explained variance, while Jöreskog’s reduced-form calculation is unnecessarily restrictive. The new blocked-error-R ² (beR ²) uses a minimal hypothetical causal intervention to resolve the variance-partitioning ambiguities created by loops and correlated errors. Hayduk (1996) discussed how stabilising feedback models – models capable of counteracting external perturbations – can result in an acceptable error variance which exceeds the variance of the dependent variable to which that error is attached. For variables included within loops, whether stabilising or not, beR ² provides the same value as Hayduk’s (1996) loop-adjusted-R ². For variables not involved in loops and not displaying correlated residuals, beR ² reports the same value as the traditional regression R ². Thus, beR ² provides a conceptualisation of the proportion of explained variance that spans both recursive and nonrecursive structural equation models. A procedure for calculating beR ² in any SEM program is provided.     

The Bell Curve in Psychological Research and Practice: Myth or Reality?

The expression “the bell curve” designs both a kind of statistical distribution and the title of a famous and controversial book by Herrnstein and Murray. The first is so attractive that the second refers to it to give more credibility to its questionable theories on intelligence. The point is that, during the 20th century, the bell curve has assumed a more and more important role in psychological research and practice and have become both a reality and a myth. In the first case (reality) we can assist to appropriate applications of a real useful statistical concept. In the second (myth) we can have two kinds of attitudes: one attitude is typical of those researchers who search for normality in all their data and variables, just as Parsifal used to search for the Holy Graal (we call this “the Parsifal attitude”); the other is typical of those researchers who give normality for granted and act as if it were a Platonic Idea (we call this “the Plato attitude”). The article discusses the role of the normal distribution in psychological research and practice and shows how it can be dangerous to treat the bell curve as a God or an Idol.     

Unemployment duration and the interactions between unemployment insurance and social assistance

Existing studies suggest that reforms that reduce the generosity of the unemployment benefits should lower unemployment. Despite the large number of such reforms implemented in Europe in the past decades, evidence from various data sources shows very little correlation with the evolution of unemployment. This paper suggests that the scant success of these labour market reforms can be explained by the interactions between unemployment insurance and other social assistance programmes. Evidence from the European Community Household Panel shows that recipients of unemployment insurance who are also eligible for other welfare schemes are indeed less sensitive to changes in the level and the duration of their benefits.     

Value and liquidity under changing market conditions

Papers studying the liquidity of a market tend to focus on decisions involving the trade-off between the selling price and the time-till-sale for a given set of market conditions. This paper characterizes market conditions using a price-probability locus; a change in market conditions is some combination of changes in the level and/or slope of this locus. I show how the effect of either type of change on price and on the probability-of-sale can be decomposed into those commonly associated with an increase in the value and those which involve a substitution between price and probability. Two adding-up conditions restrict the set of possible predictions. Though the discussion focusses on real estate market, where scarcity is rationed by a mechanism which combines search and bargaining, the same ideas apply to markets with other types of selling mechanisms.     

Efficient learning via simulation: A marginalized resample-move approach

In state–space models, parameter learning is practically difficult and is still an open issue. This paper proposes an efficient simulation-based parameter learning method. First, the approach breaks up the interdependence of the hidden states and the static parameters by marginalizing out the states using a particle filter. Second, it applies a Bayesian resample-move approach to this marginalized system. The methodology is generic and needs little design effort. Different from batch estimation methods, it provides posterior quantities necessary for full sequential inference and recursive model monitoring. The algorithm is implemented both on simulated data in a linear Gaussian model for illustration and comparison and on real data in a Lévy jump stochastic volatility model and a structural credit risk model.     

光缆自动化监测系统

介绍了远程光纤监测系统(RFTS)的结构、测试方法及其与电信管理网(TMN)的结合情况,并列举出一些典型的RFTS系统以阐明其应用和发展趋势。同时,还讨论了影响光时域反射仪(OTDR)测试精度的要素和消除测试误差通常采用的对策。     

Exact linear rank tests for two‐sample equivalence problems with continuous data

The present paper introduces a methodology for the semiparametric or non‐parametric two‐sample equivalence problem when the effects are specified by statistical functionals. The mean relative risk functional of two populations is given by the average of the time‐dependent risk. This functional is a meaningful non‐parametric quantity, which is invariant under strictly monotone transformations of the data. In the case of proportional hazard models, the functional determines just the proportional hazard risk factor. It is shown that an equivalence test of the type of the two‐sample Savage rank test is appropriate for this functional. Under proportional hazards, this test can be carried out as an exact level α test. It also works quite well under other semiparametric models. Similar results are presented for a Wilcoxon rank‐sum test for equivalence based on the Mann–Whitney functional given by the relative treatment effect.     

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.     

风险价值及压力测试在采购策略中的应用

首先分析了供应链采购风险管理的重要性,然后分别介绍了VaR和压力测试这两种风险测度方法,并在此基础上建立了采购风险度量模型,为制定科学的采购策略提供了量化的决策依据。     

浅析光纤测试技术技巧

光纤的传输速度快,对信号的输入输出起着重要的作用。在光纤布线中,信号衰减不可避免,加上其它不可知因素都对光纤测试带来很大难度。文中就光纤测试技术技巧方面展开探讨。