Properties of the weighted log‐rank test in the design of confirmatory studies with delayed effects

Proportional hazards are a common assumption when designing confirmatory clinical trials in oncology. This assumption not only affects the analysis part but also the sample size calculation. The presence of delayed effects causes a change in the hazard ratio while the trial is ongoing since at the beginning we do not observe any difference between treatment arms, and after some unknown time point, the differences between treatment arms will start to appear. Hence, the proportional hazards assumption no longer holds, and both sample size calculation and analysis methods to be used should be reconsidered. The weighted log‐rank test allows a weighting for early, middle, and late differences through the Fleming and Harrington class of weights and is proven to be more efficient when the proportional hazards assumption does not hold. The Fleming and Harrington class of weights, along with the estimated delay, can be incorporated into the sample size calculation in order to maintain the desired power once the treatment arm differences start to appear. In this article, we explore the impact of delayed effects in group sequential and adaptive group sequential designs and make an empirical evaluation in terms of power and type‐I error rate of the of the weighted log‐rank test in a simulated scenario with fixed values of the Fleming and Harrington class of weights. We also give some practical recommendations regarding which methodology should be used in the presence of delayed effects depending on certain characteristics of the trial.     

Exploring Social and Geographical Trajectories of Latin Americans in Sweden

Close to 20 percent of the Swedish population are of immigrant origin; one in eight is foreign‐born. About 45 percent of all immigrants originate from outside Europe and most of these have entered the country as refugees or relatives of refugees. Issues connected to immigration, including the number of immigrants, settlement patterns and level of social integration of ethnic minorities, have been much discussed in Sweden in recent decades. This paper focuses on the integration of Latin American immigrants in Sweden. It compares the level of integration – measured as educational achievement, labour market participation, income and housing – experienced by first and second generation migrants. I use register information allowing me to include all 1^st and 2^nd generation Latin Americans that have lived in Sweden between 1990 and 2006 (in total 127,000 individuals). Data are longitudinal, which means that individuals can be followed over time. I make use of the longitudinal material in order to study changes in residential patterns and in attempts to explain educational and employment outcomes for second generation Latin Americans. The general conclusion of the paper is that in terms of integration, LAC immigrants have an intermediate position compared to other immigrant categories; they are often better off than people from Africa and the Middle East but clearly below the level experienced by some other migrants, especially those from Western Europe. This cannot be explained by level of education. The average level of education is high for first generation immigrants from LA countries. For many people, the level of labour market participation and income increase over time but one important result of this analysis is that second generation Latin Americans seem to do less well in Sweden compared to many other second generation migrants.     

Life Experiences and Vulnerabilities of Homeless Women: A Comparison of Women Unaccompanied Versus Accompanied by Minor Children, and Correlates with Children's Emotional Distress

The histories and service needs of 2 groups of homeless women, those unaccompanied by minor children (n = 46) and those accompanied by minor children (n = 22), were compared, on the basis of their responses to a biennial survey of homeless people in a midsize city in the southeast United States. Mothers of children aged 2–10 also completed a measure of stress symptoms for their children (n = 20). Irrespective of family status group, problems such as substance abuse, history of mental illness, health problems, chronicity of homelessness, and crime victimization tended to cluster together. The findings also suggest that declining and/or inadequate levels of public benefits, Temporary Assistance to Needy Families, and Medicaid-funded health care in particular, have adversely affected the 2 groups, particularly families with children. The young children in this sample experienced elevated levels of stress, and significant associations were found between children's stress levels and certain risk factors of their mothers. Implications for service delivery are discussed.     

Wage and Non-Wage Compensation Among Young Alcoholic and Heavy Drinking Women: A Preliminary Analysis

The association between drinking and selected job characteristics among women aged 24 to 31 is examined. Using the 1989 NLSY, women are classified as alcohol abusers or dependent based on DSM-III-R criteria or as heavy drinkers based on reported frequency of six or more drinks. Heavy drinking is negatively associated with wage and non-wage compensation. These effects diminish when human capital measures are controlled. Current alcoholism and current and past heavy drinking are strongly negatively associated with years of schooling. The association between alcoholism and job compensation and characteristics is not as strong as that seen for heavy drinking. It is not known if this is a consequence of errors in identifying alcoholic women in population-based surveys.     

THE DISTRIBUTION SECTOR AND THE DEVELOPMENT PROCESS: ARE THERE PATTERNS? YES

Using an increasing returns specification for distribution, an inverted U pattern between the share of distribution in gross domestic product and the level of development is shown to arise. A cross-section time-series data set is constructed and merged with one used to analyze the service sector. In contrast to the rising pattern found for services, an average time-series relation that exhibits an inverted U pattern is established. The empirical results are robust, for example, to choice of functional form and country and time period coverage. A similar pattern is found in the average cross-section (country) relation between distribution and development.     

A NOTE ON EVANESCENT PROCESSES

This note examines the connection between μ-invariant measures for the transition function of a continuous-time Markov chain and those of its q-matrix, Q. The major result establishes a necessary and aufficient condition for a convergent μ-invariant measure for Q to be μ-inhant for the minimal transition function, P, under the assumption that P is honest. This corrects Theorem 6 of Vere-Jones (1969) and the first part of Corollary 1 of Pollett (1986), both of which assert that the above conclusion holds in the absence of this condition. The error was pointed out by E.A. van Doom (1991) and the counterexample which be presented provides the basis for the present arguments. In determining where the error occurred in the original proof, we are able to identify a simple sufficient condition for μ-invariance.     

Don't mention Stonehenge!

It rises massive and magnificent above Salisbury Plain. The extraordinary monoliths of Stonehenge leave us as impressed today as ever—and as baffled. Archaeologists argue about how it was made. Can statisticians tell the answer? Chris Jones thinks they can be of considerable assistance.     

The Politics of Integration—new Sites for Old Practices?

Public education authorities throughout the Australian States and Territories have moved towards the development of policies and programmes to integrate students considered disabled into regular classrooms. The implementation of policy frequently is reduced to disputation over resources which, it is argued, will facilitate integration. This paper contends that such debates sustain the flawed notion that integration is simply a technical issue to be achieved through deployment of special equipment and personnel to regular schools, recommending a further consideration of the contribution of pedagogy, curriculum and school organisation to disabling or enabling educational programmes.     

Female Victim Perceptions of the Causes of Male Spouse Abuse*

Victims of spouse abuse were interviewed concerning their views of why their husbands were abusive. It was hypothesized that by concentrating on one specific characteristic of this kind previously undocumented patterns of response would be elicited from the subjects. It was concluded that the women's reasons for the violence perpetrated by their spouses serve as justification for the abusers’actions and legitimize maintenance of the relationship.