On testing for causality in variance between two multivariate time series

Verifying the existence of a relationship between two multivariate time series represents an important consideration. In this article, the procedure developed by Cheung and Ng [A causality-in-variance test and its application to financial market prices, J. Econom. 72 (1996), pp. 33–48] designed to test causality in variance for univariate time series is generalized in several directions. A first approach proposes test statistics based on residual cross-covariance matrices of squared (standardized) residuals and cross products of (standardized) residuals. In a second approach, transformed residuals are defined for each residual vector time series, and test statistics are constructed based on the cross-correlations of these transformed residuals. Test statistics at individual lags and portmanteau-type test statistics are developed. Conditions are given under which the new test statistics converge in distribution towards chi-square distributions. The proposed methodology can be used to determine the directions of causality in variance, and appropriate test statistics are presented. Monte Carlo simulation results show that the new test statistics offer satisfactory empirical properties. An application with two bivariate financial time series illustrates the methods.     

Jury size and jury verdicts

The analysis of jury size and jury verdicts in criminal m a t t e r s now has along , though interrupted , history . Work In this subject in the 18th and 19th centuries by Condorcet arid Laplace is discussed and the Poisson model of the 1830's is highighted . The latter is modified t o analyze the America1 jury experience of the 20th century. Recent U. S. Supreme Court decis on sin the 1970's on jury size and jury decisiol - making have created a resurgence of interest especially on a comparison of six member and twelve member juries . Some comparisons of size in terms of probabilities of errors invericts are presented.     

An error-bounded polynomial approximation for bivariate normal probabilities

Although the bivariate normal distribution is frequently employed in the development of screening models, the formulae for computing bivariate normal probabilities are quite complicated. A simple and accurate error-bounded, noniterative approximation for bivariate normal probabilities based on a simple univariate normal quadratic or cubic approximation is developed for use in screening applications. The approximation, which is most accurate for large absolute correlation coefficients, is especially suitable for screening applications (e.g., in quality control), where large absolute correlations between performance and screening variables are desired. A special approximation for conditional bivariate normal probabilities is also provided which in quality control screening applications improves the accuracy of estimating the average outgoing product quality. Some anomalies in computing conditional bivariate normal probabilities using BNRDF and NORDF in IMSL are also discussed.     

A Capture-Recapture Problem When Information is Obtained From Two Qualitatively Different Sources

We first consider a wildlife-related capture recapture problem with a known total number of fish. Our objective is to estimate the number of healthy fish, H. We first use a rod that only attracts healthy fish, which are tagged and returned to the water. Later, we use a net that scoops both sick and healthy fish. Three assumptions regarding the probability of being caught by the net, conditional on health status and being caught by the rod, lead to three different estimates of H. We give approximations to expected values of the three estimates and give a condition under which they bracket H.

A potential application of these methods is to the follow-up of World Trade Center responders. Responders are disease-free when they arrive at the clean-up site and are asked to report for a visit after a fixed period of time, but some fail to do so. Some responders, whether they come to the scheduled return visit or not, spontaneously report a disease before the scheduled visit, but absence of disease is never reported in this manner. We use the methods developed to estimate the total number of subjects with disease by the time of the scheduled return visit.     

Construction doublebreasted operations and pre-hire agreements: Assessing the issues

Labor relations in the construction industry are conducted under a legal framework that is both different and more favorable to unions than is that in industry generally. Thus, construction employers are more subject to challenge than those in other industries if they operate both union and nonunion subsidiaries; construction unions, but not those in most other industries, may enter into agreements before anyone is hired (“pre-hire agreements”), require employees to join unions after ten days of employment instead of thirty, and require the contractor to notify them of job openings. Despite these advantages, construction unions represented only 22.2 percent of all construction workers in 1987, down from 40.1 percent in 1973, while nonunion, or “open shop,” construction accounted for more than 70 percent of the construction dollar volume as early as 1984. Attempting to overcome these trends, the construction unions have sponsored legislation in the current and last two congresses which would outlaw “doublebreasting,” i.e., one company owning both unionized and open shop subsidiaries, eliminate any restrictions on pre-hire agreements, and have the effect of forcing thousands of construction workers into unions regardless of their wishes. This article examines the reasons for the decline of construction unionism, analyzes the proposed legislation, discusses its probable impact, and concludes that it is lacking in justification for the common good.     

Use of Risk Assessment Methods in the Certification of Decontaminated Buildings

Accidental events such as fires, explosions, and leaks often result in large-scale contaminations of buildings with toxic chemicals. After decontamination, the certification for original use requires testing for residual contamination. The two basic kinds of sampling plans in use up to recently both fall short of the required performance. Their deficiencies are analyzed in terms of the scientific questions implicit in both the sampling plan and the subsequent statistical evaluation. A sampling strategy of a new kind is proposed and discussed in the same context. It is motivated by concern for the long-term safety of the building's occupants and is, therefore, based on factors important in risk assessment. Three different sampling plans are derived in the framework of this methodology, two of which have already been used in actual certification proceedings.     

Choosing among practice modalities

Summary Because of the proliferation of treatment modalities during the past decade or so, the social worker, after diagnosing his client or client-system can choose among many possible treatment models. In order to individualize the person-situation constellation as much and as well as possible, a rigorous conceptual framework is needed for this task. Many criteria will evolve as social workers expend their efforts in this direction. This paper has extracted two criteria from classical social work theory, the client's level of psychosocial maturation and his state of resistance and applied them to family therapy, group treatment, short-term treatment, and crisis intervention.     

The evaluation of a mind/body intervention to reduce psychological distress and perceived stress in college students

The authors examined the effect of a 6-week mind/body intervention on college students' psychological distress, anxiety, and perception of stress. One hundred twenty-eight students were randomly assigned to an experimental group (n = 63) or a waitlist control group (n = 65). The experimental group received 6 90-minute group-training sessions in the relaxation response and cognitive behavioral skills. The Symptom Checklist-90-Revised, Spielberger State-Trait Anxiety Inventory, and the Perceived Stress Scale were used to assess the students' psychological state before and after the intervention. Ninety students (70% of the initial sample) completed the postassessment measure. Significantly greater reductions in psychological distress, state anxiety, and perceived stress were found in the experimental group. This brief mind/body training may be useful as a preventive intervention for college students, according to the authors, who called for further research to determine whether the observed treatment effect can be sustained over a longer period of time.     

Accounting for the man-information interface in management information systems

A primary cause for the failure of both formal and informal management information systems to live up to expectations stems from the designer's lack of awareness or improper conception of the interfaces existing between information and man, its user. This underscores the need for a better understanding of the relationship between man, psychologically and sociologically, and information. The results of several experiments performed in a simulated financial setting are presented as illustrations of human information processing tendencies in both individuals and committees. Design options to attenuate human foibles and limitations and to counterveil propensities to subvert systems are discussed. Areas for further research are suggested.