Non-ignorable missing covariate data in survival analysis: a case-study of an International Breast Cancer Study Group trial

Summary.  Non-ignorable missing data, a serious problem in both clinical trials and observational studies, can lead to biased inferences. Quality-of-life measures have become increasingly popular in clinical trials. However, these measures are often incompletely observed, and investigators may suspect that missing quality-of-life data are likely to be non-ignorable. Although several recent references have addressed missing covariates in survival analysis, they all required the assumption that missingness is at random or that all covariates are discrete. We present a method for estimating the parameters in the Cox proportional hazards model when missing covariates may be non-ignorable and continuous or discrete. Our method is useful in reducing the bias and improving efficiency in the presence of missing data. The methodology clearly specifies assumptions about the missing data mechanism and, through sensitivity analysis, helps investigators to understand the potential effect of missing data on study results.     

Statistics for weighing benefits and harms in a proposed genetic substudy of a randomized cancer prevention trial

Summary.  When evaluating potential interventions for cancer prevention, it is necessary to compare benefits and harms. With new study designs, new statistical approaches may be needed to facilitate this comparison. A case in point arose in a proposed genetic substudy of a randomized trial of tamoxifen versus placebo in asymptomatic women who were at high risk for breast cancer. Although the randomized trial showed that tamoxifen substantially reduced the risk of breast cancer, the harms from tamoxifen were serious and some were life threaten-ing. In hopes of finding a subset of women with inherited risk genes who derive greater bene-fits from tamoxifen, we proposed a nested case–control study to test some trial subjects for various genes and new statistical methods to extrapolate benefits and harms to the general population. An important design question is whether or not the study should target common low penetrance genes. Our calculations show that useful results are only likely with rare high penetrance genes.     

Real nonparametric regression using complex wavelets

Summary.  Wavelet shrinkage is an effective nonparametric regression technique, especially when the underlying curve has irregular features such as spikes or discontinuities. The basic idea is simple: take the discrete wavelet transform of data consisting of a signal corrupted by noise; shrink or remove the wavelet coefficients to remove the noise; then invert the discrete wavelet transform to form an estimate of the true underlying curve. Various researchers have proposed increasingly sophisticated methods of doing this by using real-valued wavelets. Complex-valued wavelets exist but are rarely used. We propose two new complex-valued wavelet shrinkage techniques: one based on multiwavelet style shrinkage and the other using Bayesian methods. Extensive simulations show that our methods almost always give significantly more accurate estimates than methods based on real-valued wavelets. Further, our multiwavelet style shrinkage method is both simpler and dramatically faster than its competitors. To understand the excellent performance of this method we present a new risk bound on its hard thresholded coefficients.     

'The Tribunal was the most stressful thing: more stressful than my son's diagnosis or behaviour': the experiences of families who go to the Special Educational Needs and Disability Tribunal (SENDisT)

It is more than 10 years since the Special Educational Needs Tribunal was established in 1994 as an independent panel which arbitrates in disputes between parents of children with the label special educational needs and Local Education Authorities (LEAs) in England. In 2002 the Tribunal began hearing claims for disability discrimination and was re-named the Special Educational Needs and Disability Tribunal (SENDisT). Since 1994 over 20,000 appeals have been registered. This article, which forms part of my ongoing Ph.D. thesis 'Parents as advocates: the experience of parents who register an appeal with SENDisT', offers an analysis of parents' Tribunal stories. Here, the key question is what affect the process of going to SENDisT has on the social, emotional and financial well-being of the family. Through a process of narrative inquiry the aim is to foreground parents' unheard stories and to reveal their 'hidden' experiences.     

Struggles with Time: the careers of parents with adult sons and daughters with learning disabilities

The experiences of parents with adult offspring with learning disability and the meanings their parental careers have for them, has been the subject of very little empirical research. In this paper we describe and examine some of the features that gave shape and meaning to the day to day lives of parents of 33 co-resident adults with learning disabilities. Their accounts of their situations revealed that 'time' was a factor of some importance. Participants suggested that socialisation into the parental role was one that continued over the life course. In addition, they also felt that the services they received were based upon an inadequate and too narrow an understanding of how they experienced 'time'. The data reveal that both 'over time' and 'in time', parents struggled to maintain a set of aspirations for a typical life. The data show that for many parents there was a slow accommodation to the constraints of service provision and, as a result, their needs for service support became less extensive.     

Unjust Freedom: The Ethics of Client Self-Determination in Runaway Youth Shelters

Client self-determination has been called the most confounding and professionally debilitating concept of all the intellectual principles under-girding social work (Rothman, 1989). Identifying the appropriate parameters of client self-determination is a particularly acute problem for social workers employed by runaway and homeless youth shelters where minors are making adult decisions free from parental guidance. We examine the ethical dimensions of practice with minor clients in runaway shelters by arguing that a conflict exists between the liberty-based principle of self-determination and the justice-based notion of client competency. We analyze the conflict by using minimal distributive justice as the organizing principle of social work practice. We conclude that client self-determination in runaway shelters should be restricted and that presuming client competence violates the basic value tenets of the profession.     

Let Me Go: The Influences of Crawling Experience and Temperament on the Development of Anger Expression

Infants’ emerging ability to move independently by crawling is associated with changes in multiple domains, including an increase in expressions of anger in situations that block infants’ goals, but it is unknown whether increased anger is specifically because of experience with being able to move autonomously or simply related to age. To examine the influence of locomotion on developmental change in anger, infants’ (N = 20) anger expressions during an arm restraint procedure were observed longitudinally at a precrawling baseline assessment and 2 and 6 weeks after the onset of crawling. Infant age at each crawling stage was unrelated to the frequency of anger expressed in response to arm restraint. At 6 weeks postcrawling onset, infants whose mothers rated them as temperamentally higher in distress to limitations, compared with those rated lower, showed a greater increase in the frequency of anger expressed during the arm restraint relative to earlier assessments and took longer to reduce the frequency of anger expressed when no longer restrained. Findings suggest that experience with autonomous crawling has an effect on anger expression, independent of age, and that a temperamental tendency to become distressed by limitations may exacerbate the effect of crawling on anger expression.