Disentangling the sources of variation in the survival of the European dipper

The population growth rate of the European dipper has been shown to decrease with winter temperature and population size. We examine here the demographic mechanism for this effect by analysing how these factors affect the survival rate. Using more than 20 years of capture-mark-recapture data (1974-1997) based on more than 4000 marked individuals, we perform analyses using open capture-mark-recapture models. This allowed us to estimate the annual apparent survival rates (probability of surviving and staying on the study site from one year to the next one) and the recapture probabilities. We partitioned the variance of the apparent survival rates into sampling variance and process variance using random effects models, and investigated which variables best accounted for temporal process variation. Adult males and females had similar apparent survival rates, with an average of 0.52 and a coefficient of variation of 40%. Chick apparent survival was lower, averaging 0.06 with a coefficient of variation of 42%. Eighty percent of the variance in apparent survival rates was explained by winter temperature and population size for adults and 48% by winter temperature for chicks. The process variance outweighed the sampling variance both for chick and adult survival rates, which explained that shrunk estimates obtained under random effects models were close to MLE estimates. A large proportion of the annual variation in the apparent survival rate of chicks appears to be explained by inter-year differences in dispersal rates.     

Is Unemployment a Health Hazard? Health-related behaviours of a sample of unemployed Sydney youth in 1980

A self-report questionnaire, tapping a variety of areas of health-related behaviours, was administered individually to a hundred young men and women aged between 15 and 24 years, solicited outside the Commonwealth Employment Service Office in Liverpool, New South Wales, in August 1980, all of whom described themselves as having been continuously unemployed for at least four weeks up to the time of interview. The group was divided at its approximate median of five months in terms of duration of current period of unemployment, and the short-term and long-term unemployed groups thus derived were contrasted on all variables. The resultant analysis showed the total long-term unemployed group to be characterized by heavier smoking, reduced participation in sport, and, though not statistically significant, increased drug usage, relative to the short-term group. Within the long-term group, females were drinking more, and visiting the doctor more, than their short-term peers; males were changing their drinking, friendship, eating and sleeping habits in directions indicative of loss of social contact.     

Measuring the impact of child mortality on fertility: A methodological note

Recent studies of the impact of child mortality on children ever born have used the “replacement factor” to measure mortality. When microlevel data are used, however, use of the replacement factor (or other variables which are nonlinear in the family’s experienced child mortality rate) yields biased coefficients. An alternative model suggests a sequential, rather than a static, decision-making process to relate the decision to have an additional child to the reproductive experience to date. In this case, unbiased coefficients are obtained if the functional form is correctly specified. In the absence of a priori knowledge of the functional form, it is difficult to untangle true effects from spurious ones.     

An Interactive Forecasting System

Time sharing computer configurations have introduced a new dimension in applying statistical and mathematical models to sequential decision problems. When the outcome of one step in the process influences subsequent decisions, then an interactive time-sharing system is of great help. Since the forecasting function involves such a sequential process, it can be handled particularly well with an appropriate time-shared computer system. This paper describes such as system which allows the user to do preliminary analysis of his data to identify the forecasting technique or class of techniques most appropriate for his situation and to apply those in developing a forecast. This interactive forecasting system has met with excellent success both in teaching the fundamentals of forecasting for business decision making and in actually applying those techniques in management situations.     

A comparison of alternative variance estimation strategies for estimating the slope of a linear regression in sample surveys

The balanced half-sample, jackknife and linearization methods are used to estimate the variance of the slope of a linear regression under a variety of computer generated situations. The basic sampling design is one in which two PSU's are selected from each of a number of strata . The variance estimation techniques are compared with a Monte Carlo experiment. Results show that variance estimates may be highly biased and variable unless sizeable numbers of observations are available from each stratum. The jackknife and linearization estimates appear superior to the balanced half sample method - particularly when the number of strata or the number of available observations from each stratum is small.     

Investigation of disease-free survival as a surrogate endpoint for survival in cancer clinical trials

A stochastic model wiuh exponential components is used to describe our data collected from a phase III cancer clinical trial. Criteria which guarantee that disease-free survival (DFS) can be used as a surrogate for overall survival are explored under this model. We examine several colorectal adjuvant clinical trials and find that these conditions are not satisfied. The relationship between the hazard ratio of DFS for an active treatment versus a control treatment and the cumulative hazard ratio of survival for the same two treatments is then explored. An almost linear relationship is found such that a hazard ratio for DFS of less than a threshold R corresponds to a non-null treatment effect on survival The threshold value R is determined for our colorectal adjuvant trial data. Based on this relationship, a one-sided test of equal hazard rate of survival is equivalent to a test of hazard ratio of DFS small than R This approach assumes that recurrence information is unbiasedly and accurately assessed; an assumpion which is sometimes difficult to ensure for multicenter clinical trials, particularly for interim analyses.     

Redefining Neighborhoods Using Common Destinations: Social Characteristics of Activity Spaces and Home Census Tracts Compared

Research on neighborhood effects has focused largely on residential neighborhoods, but people are exposed to many other places in the course of their daily lives—at school, at work, when shopping, and so on. Thus, studies of residential neighborhoods consider only a subset of the social-spatial environment affecting individuals. In this article, we examine the characteristics of adults’ “activity spaces”—spaces defined by locations that individuals visit regularly—in Los Angeles County, California. Using geographic information system (GIS) methods, we define activity spaces in two ways and estimate their socioeconomic characteristics. Our research has two goals. First, we determine whether residential neighborhoods represent the social conditions to which adults are exposed in the course of their regular activities. Second, we evaluate whether particular groups are exposed to a broader or narrower range of social contexts in the course of their daily activities. We find that activity spaces are substantially more heterogeneous in terms of key social characteristics, compared to residential neighborhoods. However, the characteristics of both home neighborhoods and activity spaces are closely associated with individual characteristics. Our results suggest that most people experience substantial segregation across the range of spaces in their daily lives, not just at home.     

The Nature and Effects of Young Children's Lies

Children's use of deception in a naturalistic setting was observed longitudinally in 40 families when children were 2 and 4 years old, and again two years later. Goals included describing children's lying behavior and parents’ reactions to lies, and comparing lies to other false statements. Lies were commonly told to avoid responsibility for transgressions, to falsely accuse siblings, and to gain control over another's behavior. Unlike children's other false statements (e.g., mistakes, pretense), lies were distinctly self‐serving. Parents rarely addressed the act of lying itself but often challenged the veracity of lies or addressed the underlying transgression. Older siblings lied more often than younger ones, and parents who allowed older siblings to lie at Time 1 had children who lied more often at Time 2. Results are considered from a speech‐act perspective and in terms of children's developing understanding of mental states.     

Food Aid in Complex Emergencies: Lessons from Sudan

The term "complex emergency" was coined by the UN to imply a phenomenon characterized by a combination of causes (conflicts, war, famine, displacement) requiring a combination of responses (military, peacekeeping, relief ). The "complexity" refers to the "multi–mandate" nature of the response as well as the multi–causal nature of the emergency. Operation Lifeline Sudan (OLS), the UN humanitarian assistance programme in Sudan, has been described as history's largest humanitarian intervention in an active civil war, providing a model for the international community in what can be achieved in complex political emergencies. The paper reviews how humanitarian aid was used in Sudan, and the potential for that usage contributing to development. The political dimension of decisions taken and implemented by donors, the United Nations and non–governmental organizations is explored.     

Gender, social capital and location: understanding the interactions

In recent years, governments in many post-industrial nations have re-discovered 'community'. Social capital and neighbourhood renewal are key concepts underpinning policies aimed at building the capacities of communities to respond to the problems facing them. Despite the apparent consensus amongst Anglo-American governments about the use of social capital, and related concepts, as a guide for policy formulation these ideas remain hotly contested amongst social policy commentators. Against a general backdrop of disquiet about the application of social capital initiatives to communities facing significant social and economic challenges, some commentators highlight the curious inattention to gender in debates about social capital. This is all the more troubling given the apparent reliance of social capital initiatives on the informal network-building activities often undertaken by women. In this article we present findings from an empirical study of social capital creation across four geographically diverse communities. We show that the relationship between gender and social capital is complex. We argue that the 'one-size-fits-all' approach to social capital formulation fails to recognise gendered patterns of social capital formulation, but so, too, do analyses of gender that neglect the complex interactions between gender and other factors, particularly location, age and income. We argue for approaches to policy formulation that recognise local differences, including differences between and amongst men and women in social capital creation.