Cox regression analysis in presence of collinearity: an application to assessment of health risks associated with occupational radiation exposure

This paper considers the analysis of time to event data in the presence of collinearity between covariates. In linear and logistic regression models, the ridge regression estimator has been applied as an alternative to the maximum likelihood estimator in the presence of collinearity. The advantage of the ridge regression estimator over the usual maximum likelihood estimator is that the former often has a smaller total mean square error and is thus more precise. In this paper, we generalized this approach for addressing collinearity to the Cox proportional hazards model. Simulation studies were conducted to evaluate the performance of the ridge regression estimator. Our approach was motivated by an occupational radiation study conducted at Oak Ridge National Laboratory to evaluate health risks associated with occupational radiation exposure in which the exposure tends to be correlated with possible confounders such as years of exposure and attained age. We applied the proposed methods to this study to evaluate the association of radiation exposure with all-cause mortality.     

AN EMPIRICAL EXAMINATION OF SOCIAL POWER IN TERMS OF DECISION THEORY1

The paper presents an extension of decision theory to the analysis of social power. The power of a person, A, over another person, B, is viewed in terms of the effect A has on B's decision. The analysis is based on the idea that B's decision regarding the performance of alternative behaviors is a function of 1) B's utility for the consequences of the behaviors and 2) B's subjective probabilities that the behaviors will lead to these consequences. In these terms, A's power over B lies in A's ability to mediate various consequences for B, contingent upon B's compliance or noncompliance. Subjects were asked to consider eight situations in which hypothetical individuals had to make a choice between two courses of action. In each situation another person (A) was attempting to induce the hypothetical individual (B) to choose one of the alternatives, while various situational factors were influencing B to choose the other alternative. The subjects were asked to consider B's utilities and subjective probabilities in each situation and to indicate whether or not B should comply with A and to make ratings of A's power. The decision theory analysis did well in predicting whether or not subjects would indicate that B should comply with A. Also, subjects generally were able to correctly specify whether A or the situational factors had more influence over B's decision. Finally, the subjects' ratings of A's power in the eight situations were highly related to the decision theoretic measure of power.     

Advanced Behavioral Applications in Schools: A Review of R. Douglas Greer’s Designing Teaching Strategies: An Applied Behavior Analysis Systems Approach

The Analysis of Verbal Behavior - R. Douglas Greer1s Designing Teaching Strategies is an important book directed to advanced students in applied behavior analysis for classrooms. This review...     

The role of small firms in the emergence of new technologies

It is clear from research policy statements throughout Europe and in the USA and Japan that governments are becoming increasingly interested in the well-being of small firms. This is based on a belief in their ability to generate employment, their potential for the industrial regeneration of the so-called development areas and their ability to produce technological innovations. It is to this latter issue—the innovation potential of small firms—that this article is addressed. Further, while most studies of the role of small firms in innovation have been concerned with ‘innovation counts’ and have adopted a rather static approach, we are here concerned with their role in the dynamics of the introduction and diffusion of new technologies, specifically semiconductors and computer aided design (CAD). Moreover, there has in the past been a tendency to emphasize the role of the small firms or the role of large firms in innovation; we reject this rather sterile view and demonstrate the interrelationship between the two. In both areas—semiconductors and CAD—the initial breakthroughs were made in the R&D laboratories of large companies which produced components and equipment for their own use; it was through the actions of new technology-based small firms that these innovations were diffused into more general use. Again in both cases, the basic technological know-how, the entrepreneurs themselves and often the risk capital, derived from the original innovating large companies. Thus, policies that do not take into account the dynamic complementarities between the large and the small clearly are of only limited utility.     

Problem-based Learning: Potential and Implementation Issues

This study addresses the issues associated with the application of problem-based learning, examines the key design dimensions of a problem-based learning course and considers the implications of problem-based learning for learners and educators.     

On the identification of ARMA echelon-form models

An identification procedure for multivariate autoregressive moving average (ARMA) echelon-form models is proposed. It is based on the study of the linear dependence between rows of the Hankel matrix of serial correlations. To that end, we define a statistical test for checking the linear dependence between vectors of serial correlations. It is shown that the test statistic t?_n considered is distributed asymptotically as a finite linear combination of independent chi-square random variables with one degree of freedom under the null hypothesis, whereas under the alternative hypothesis, t?_N/N converges in probability to a positive constant. These results allow us, in particular, to compute the asymptotic probability of making a specification error with the proposed procedure. Links to other methods based on the application of canonical analysis are discussed. A simulation experiment was done in order to study the performance of the procedure. It is seen that the graphical representation of t?_N, as a function of N, can be very useful in identifying the dynamic structure of ARMA models. Furthermore, for the model considered, the proposed identification procedure performs very well for series of 100 observations or more and reasonably well with short series of 50 observations.     

Interethnic marriage: identifying the second generation in Australia

"Studies in Australia show that an increasing proportion of the population have ancestors from more than one country. Evidence regarding differences in the marriage patterns of first and second generation migrants has been restricted in scope as published marriage registration data includes only birthplace of partners. Marriage registration records include information about the birthplace of parents of partners, but is available only through specially produced tabulations. Changes in the census for 1986 and 1991 make it possible to identify the second generation in households, and this article examines the use of census data as an alternative to marriage registration records in tracing changes in intermarriage patterns and differences between urban and rural areas."     

Population estimates for Bangladesh: The use of a specific transitional population model

Summary The development of population in Bangladesh was affected by a succession of man-made and natural calamities, such as the Bengal Famine of 1943, refugee movements following the partition of India and Pakistan in 1947, devastating floods and cyclones around 1970, and the military action during the war of liberation. Though there had been a tradition of census taking and vital registration in Bangladesh, as part of the Indian sub-continent, extending for over a century, vital registration was so deficient as to be almost valueless, and there were gross misstatements of age and under-enumeration in the censuses. In the census of 1941, on the other hand, political manoeuvring led to a substantial overcount of the population. In this paper, Bangladesh population trends are studied within the broader framework of the subcontinent, taking account of plausible differentials. A considerable element of uncertainty was introduced into growth trends as a result of variations in the completeness of census-taking and of unrecorded refugee and labour movements across open land borders. In this connection the substantial inflationary bias associated with techniques of population estimation using the dual record system is discussed. The application of stable population models is even less justified in Bangladesh with its history of declining mortality. A transitional age structure model was constructed on the basis of the information available on declining mortality and accelerating growth and the model was made even more specific by modifications which took care of the impact of recent calamities and of unrecorded migration. The population base of the census of 1961 was adjusted in accordance with this model. The local mortality age pattern was used in projecting the population by sex and age groups to the date at which the census was originally due to be taken in 1971, and to the date when it was actually taken in March 1974. The post-1970 calamities and their effect on mortality were ignored. The aggregate estimate of population of 72.9 million in March 1974 is slightly in excess of the census count (by about two per cent) reported provisionally as 71.3 million. The excess in our estimate could be accounted for by the losses due to cyclone and military action.     

Beyond friendship: the nature and meaning of close personal relationships as perceived by people with learning disabilities

Many people with learning disabilities aspire to having friends and to forming close relationships. Often the latter are discouraged, but for those who enter into such a relationship little is known about the meaning and value it brings to their lives. The aim of this study was to gain an insight into the close relationships of eight couples with learning disabilities using a combination of dyadic and one-to-one interviews. Data collection and analysis was informed and guided by the core principles of grounded theory. Five significant types of benefits were identified from having close personal relationships, namely: comradeship, a sense of contentment, availability of mutual support, coping with the ups and downs of relationships, and a continuing commitment. Service providers could do more to facilitate the formation of close meaningful relationships, and strategies for doing this need to be identified and evaluated.