Pre-term Foetal Life Times in Scotland

A proportional hazards model was used to evaluate the association between ten categorical covariates and the risk of pre-term delivery for women having their first child and women in subsequent pregnancies. An adaptation of the model for use with grouped survival times made it possible to model foetal life times between 28 and 36 completed weeks of gestation for 67,000 Scottish singleton births in 1981. The use of the model was justified by testing time-dependent effects. For both groups of women age, and a history of abortion, were major factors associated with increased hazard. For women experiencing a second or higher-order birth a history of perinatal death was also associated with substantially increased hazard to the pregnancy.     

On sequential closed testing dose groups with a control

Methods for a sequential test of a dose-response effect in pre-clinical studies are investigated. The objective of the test procedure is to compare several dose groups with a zero-dose control. The sequential testing is conducted within a closed family of one-sided tests. The procedures investigated are based on a monotonicity assumption. These closed procedures strongly control the familywise error rate while providing information about the shape of the dose-responce relationship. Performance of sequential testing procedures are compared via a Monte Carlo simulation study. We illustrae the procedures by application to a real data set.     

Income Diversity,Technology Choice and Agricultural Research Policy in Sub‐Saharan Africa

This article makes an initial analysis of the implications of income diversification for technical change and agricultural research policy in Africa, leading to two insights. First, that the dilution effect of income diversification means that, as the proportion of non‐farm income increases, so must the expected gains from adopting a new agricultural technology. Second, that diversified producers will face disproportionately large transactions costs associated with information acquisition to inform technology choice decisions. Two hypotheses about how diversified producers are likely to react are then explored. Both point to the conclusion that income diversification among the poor is likely to constrain significantly the direct poverty impacts of agricultural research. The policy implications of these findings are then considered.     

Minimax property of stein's estimator

Stein's estimator and some other estimators of the mean of a K-variate normal distribution are known to dominate the maximum likelihood estimator under quadratic loss for K > 3, and are therefore minimax. In this paper it is shown that the minimax property of Stein's rule is preserved with respect to a generalized loss function.     

Applications of Theories of Group Processes

Theories of group processes have been and are being applied usefully to natural situations. We review a selection of these theories and examine different types of applications and interventions to which they have led. We then offer a typology of application, five "stages" with examples. As theoretical application proceeds, issues of complexity, rules of correspondence, and competing social interests increase the difficulty of that work, yet the benefits are considerable for theoretical development.     

Cast in a racial mould

Women of Phokeng: Consciousness, Life Strategy, and Migrancy in South Africa 1900 ‐1983 by Belinda Bozzoli, with the assistance of Mmantho Nkotsoe, Johannesburg, Ravan Press, 1991.

Our Precious Metal: African Labour in South Africa's Gold Industry, 1970–1990 by Wilmot G. James, David Philip, James Currey &; Indiana University Press, Cape Town, London &; Bloomington,1992.

Bounds of Possibility ‐ The Legacy of Steve Biko &; Black Consciousness by N.B. Pityana, M. Ramphele, M. Mpumlwana, &; L. Wilson, (eds), Cape Town, David Philip, 1991.

Faces in the revolution: the psychological effects of violence on township youth in South Africa by Gill Straker, with Fathima Moosa, Rise Becker and Madiyoyo Nkwale. Cape Town, David Philip, 1992 and Athens, Ohio, Ohio University Press, 1992.

Lives of Courage: Women for a New South Africa by Diana E.H.Russell. New York, Basic Books, 1989.

Towards Justice? Crime and State Control in South Africa by Desiree Hansson and Dirk van Zyl Smit (eds), Cape Town, Oxford University Press, 1990.

South Africa in the Nineties by DJ van Vuuren, NE Wiehahn, NJ Rhoodie en M Wiechers (eds), HSRC Publishers, 1991.

To Live in Fear: Witchburning and Medicine Murder in Venda by A de V. Minnar, D Offringa and C Payze, HSRC, Pretoria, 1992.

The Anti‐Politics Machine: ‘Development’, Depoliticization and Bureaucratic Power by James Ferguson, Cambridge, Cambridge University Press, 1990.

Zimbabwe's Guerrilla War: Peasant Voices by Norma J. Kriger. Cambridge University Press, African Studies Series, number 70,1992.

A Passage to England ‐ Barbadian Londoners speak of home by John Western. U.C.L. Press, London, 1992.

Breaking the formal frame: Readings in South African education in the eighties by Clive Millar, Sarah‐Anne Raynham and Angela Schaffer (eds). Cape Town: Oxford University Press, 1991.

Negotiation : Theories, Strategies and Skills by Wynand Pienaar and Manie Spoelstra, Kenwyn, Juta, 1991

SUM: Selected Works by Martin Versveld. Cape Town: Carrefour Press 1991.

Projections in the Past Tense, by Kelwyn Sole. Ravan Press, 1992.     

A long way from home: On black identity in Britain

This article sets out to challenge much of the current literature on the self‐identity of blacks in British society. By looking at the long‐term historical background, the colonial heritage of cultural, political and economic oppression, a series of more subtle analyses emerges. Among the stereotypes challenged is that of the generational gap; evidence is cited to indicate a far greater common awareness and identity of aims and attitudes than previous writers have suggested. Hie conclusion examines some strategies for fighting racism within British society.     

Sign Restrictions,Structural Vector Autoregressions,and Useful Prior Information

This paper makes the following original contributions to the literature. (i) We develop a simpler analytical characterization and numerical algorithm for Bayesian inference in structural vector autoregressions (VARs) that can be used for models that are overidentified, just‐identified, or underidentified. (ii) We analyze the asymptotic properties of Bayesian inference and show that in the underidentified case, the asymptotic posterior distribution of contemporaneous coefficients in an n‐variable VAR is confined to the set of values that orthogonalize the population variance–covariance matrix of ordinary least squares residuals, with the height of the posterior proportional to the height of the prior at any point within that set. For example, in a bivariate VAR for supply and demand identified solely by sign restrictions, if the population correlation between the VAR residuals is positive, then even if one has available an infinite sample of data, any inference about the demand elasticity is coming exclusively from the prior distribution. (iii) We provide analytical characterizations of the informative prior distributions for impulse‐response functions that are implicit in the traditional sign‐restriction approach to VARs, and we note, as a special case of result (ii), that the influence of these priors does not vanish asymptotically. (iv) We illustrate how Bayesian inference with informative priors can be both a strict generalization and an unambiguous improvement over frequentist inference in just‐identified models. (v) We propose that researchers need to explicitly acknowledge and defend the role of prior beliefs in influencing structural conclusions and we illustrate how this could be done using a simple model of the U.S. labor market.     

THE BALANCED US PRESS

We measure the relative ideological positions of newspapers, voters, interest groups, and political parties, using data on ballot propositions. We exploit the fact that newspapers, parties, and interest groups take positions on these propositions, and the fact that citizens ultimately vote on them. We find that, on average, newspapers in the United States are located almost exactly at the median voter in their states—that is, they are balanced around the median voter. Still, there is a significant amount of ideological heterogeneity across newspapers, which is smaller than the one found for interest groups. However, when we group propositions by issue area, we find a sizable amount of ideological imbalance: broadly speaking, newspapers are to the left of the state‐level median voter on many social issues, and to the right on many economic issues. To complete the picture, we use two existing methods of measuring bias and show that the news and editorial sections of newspapers have almost identical partisan positions.     

Effects of a single-lesson tobacco prevention curriculum on knowledge, skill identification and smoking intention

One in five students report experimenting with tobacco before the age of 13 and most prevention efforts take place in the school setting. This study measures the effect of a single-lesson tobacco prevention curriculum, conducted by a health education center, focusing on knowledge of tobacco, ability to identify refusal techniques, and intent not to smoke. Data were collected, via electronic keypads, from students visiting a non-school, health education center in Michigan (n = 704 intervention and 85 comparison). Contingency table Chi-squared tests and t-tests demonstrated that a single lesson can improve general knowledge and ability to identify appropriate refusal techniques. Improvement in intent not to smoke was not significant because both groups had very high intent prior to implementation. Similar to results from other programs, multivariate logistic regression of gender, general knowledge, and skill identification revealed that only the skill variable was associated with intent not to smoke at pretest. Recommendations are given for further research and for designing more effective curricula or programs.