Missing item imputation for quality-of-life instruments with application to asthma quality-of-life questionnaires

There has been increasing use of quality-of-life (QoL) instruments in drug development. Missing item values often occur in QoL data. A common approach to solve this problem is to impute the missing values before scoring. Several imputation procedures, such as imputing with the most correlated item and imputing with a row/column model or an item response model, have been proposed. We examine these procedures using data from two clinical trials, in which the original asthma quality-of-life questionnaire (AQLQ) and the miniAQLQ were used. We propose two modifications to existing procedures: truncating the imputed values to eliminate outliers and using the proportional odds model as the item response model for imputation. We also propose a novel imputation method based on a semi-parametric beta regression so that the imputed value is always in the correct range and illustrate how this approach can easily be implemented in commonly used statistical software. To compare these approaches, we deleted 5% of item values in the data according to three different missingness mechanisms, imputed them using these approaches and compared the imputed values with the true values. Our comparison showed that the row/column-model-based imputation with truncation generally performed better, whereas our new approach had better performance under a number scenarios.     

Reliability acceptance sampling plans for the Weibull distribution under accelerated Type-I censoring

Type-I censored reliability acceptance sampling plans (RASPs) are developed for the Weibull lifetime distribution with unknown shape and scale parameters such that the producer and consumer risks are satisfied. It is assumed that the life test is conducted at an accelerated condition for which the acceleration factor (AF) is known, and each item is continuously monitored for failure. Sensitivity analyses are also conducted to assess the effect of the uncertainty in the assumed AF on the actual producer and consumer risks, and a method is developed for constructing RASPs that can accommodate the uncertainty in AF.     

Active‐controlled,non‐inferiority trials in oncology: arbitrary limits,infeasible sample sizes and uninformative data analysis. Is there another way?

In oncology, it may not always be possible to evaluate the efficacy of new medicines in placebo-controlled trials. Furthermore, while some newer, biologically targeted anti-cancer treatments may be expected to deliver therapeutic benefit in terms of better tolerability or improved symptom control, they may not always be expected to provide increased efficacy relative to existing therapies. This naturally leads to the use of active-control, non-inferiority trials to evaluate such treatments. In recent evaluations of anti-cancer treatments, the non-inferiority margin has often been defined in terms of demonstrating that at least 50% of the active control effect has been retained by the new drug using methods such as those described by Rothmann et al., Statistics in Medicine 2003; 22:239-264 and Wang and Hung Controlled Clinical Trials 2003; 24:147-155. However, this approach can lead to prohibitively large clinical trials and results in a tendency to dichotomize trial outcome as either 'success' or 'failure' and thus oversimplifies interpretation. With relatively modest modification, these methods can be used to define a stepwise approach to design and analysis. In the first design step, the trial is sized to show indirectly that the new drug would have beaten placebo; in the second analysis step, the probability that the new drug is superior to placebo is assessed and, if sufficiently high in the third and final step, the relative efficacy of the new drug to control is assessed on a continuum of effect retention via an 'effect retention likelihood plot'. This stepwise approach is likely to provide a more complete assessment of relative efficacy so that the value of new treatments can be better judged.     

Identifying the most successful dose (MSD) in dose-finding studies in cancer

For a dose finding study in cancer, the most successful dose (MSD), among a group of available doses, is that dose at which the overall success rate is the highest. This rate is the product of the rate of seeing non-toxicities together with the rate of tumor response. A successful dose finding trial in this context is one where we manage to identify the MSD in an efficient manner. In practice we may also need to consider algorithms for identifying the MSD which can incorporate certain restrictions, the most common restriction maintaining the estimated toxicity rate alone below some maximum rate. In this case the MSD may correspond to a different level than that for the unconstrained MSD and, in providing a final recommendation, it is important to underline that it is subject to the given constraint. We work with the approach described in O'Quigley et al. [Biometrics 2001; 57(4):1018-1029]. The focus of that work was dose finding in HIV where both information on toxicity and efficacy were almost immediately available. Recent cancer studies are beginning to fall under this same heading where, as before, toxicity can be quickly evaluated and, in addition, we can rely on biological markers or other measures of tumor response. Mindful of the particular context of cancer, our purpose here is to consider the methodology developed by O'Quigley et al. and its practical implementation. We also carry out a study on the doubly under-parameterized model, developed by O'Quigley et al. but not     

Fathering With Multiple Partners: Links to Children's Well‐Being in Early Childhood

The claim that multiple partner fertility may pose a risk of adverse outcomes for children has not been tested. We test this argument using a sample of 4,027 resident fathers and children from the Fragile Families and Child Well‐being Survey by examining the pathways through which fathers' multipartnered fertility is associated with children's externalizing behaviors and physical health status at 36 months. Path analyses indicate that multiple partner fertility exerted both a significant direct and indirect effect through paternal depression to influence children's externalizing behaviors. Fathers' multiple partner fertility also exerted a significant indirect effect through one mediator—father involvement—to influence children's physical health. This evidence suggests that the disruptions brought about by multipartnered fertility are important for understanding child well‐being.     

Promoting Fathers' Engagement With Children: Preventive Interventions for Low‐Income Families

Few programs to enhance fathers' engagement with children have been systematically evaluated, especially for low‐income minority populations. In this study, 289 couples from primarily low‐income Mexican American and European American families were randomly assigned to one of three conditions and followed for 18 months: 16‐week groups for fathers, 16‐week groups for couples, or a 1‐time informational meeting. Compared with families in the low‐dose comparison condition, intervention families showed positive effects on fathers' engagement with their children, couple relationship quality, and children's problem behaviors. Participants in couples' groups showed more consistent, longer term positive effects than those in fathers‐only groups. Intervention effects were similar across family structures, income levels, and ethnicities. Implications of the results for current family policy debates are discussed.     

Stepfamily Formation: Implications for Adolescent Ties to Mothers,Nonresident Fathers,and Stepfathers

This study examines how the entrance of a stepfather influences adolescent ties to mothers and nonresident fathers and how prior ties to each biological parent influence the development of stepfather‐stepchild ties. Data come from 1,753 adolescents in the National Longitudinal Study of Adolescent Health who lived with a single mother in Wave 1 who remained single, cohabited, or married by Wave 2, approximately 1 year later. Stepfamily formation had little consequence for adolescent‐nonresident father ties. Adolescent‐mother closeness, however, declined when cohabiting, but not married, stepfathers entered the household. Close ties to married stepfathers were more likely to develop when adolescents were closer to their mothers before stepfather entry. Prior ties to nonresident fathers were unrelated to stepfather‐stepchild ties.     

Women's “Justification” of Domestic Violence in Egypt

We explored the influences of women's social learning, marital resources and constraints, and exposure to norms about women's family roles on their views about wife hitting or beating among 5,450 participants in the 2005 Egypt Demographic and Health Survey. One half justified wife hitting or beating for some reason. Women from rural areas who were exposed to domestic violence more often justified such acts. Dependent wives whose husbands had more schooling, were blood relatives, and were coresident more often justified such acts. In settings where women tended to marry at older ages, women less often justified such acts. Women's resources and constraints in marriage accounted for the largest share of the variability in their attitudes about domestic violence against women.     

‘Allowed into a Man's World’ Meanings of Work–Life Balance: Perspectives of Women Civil Engineers as ‘Minority’ Workers in Construction

This article discusses how women working as civil engineers within the UK construction industry perceive work–life balance and considers strategies they use to achieve this. The findings are presented of a qualitative research project that explored the experiences of women in this role, focusing on the subcultural context of a profession that is dominated by the values of presenteeism and infinite availability. A feminist post‐structuralist framework is used to analyse how women negotiate their personal and professional time and the extent to which their other roles as carers and nurturers unsettle male work practices in this highly gendered profession. There are gradually increasing numbers of women in professional construction roles and their success appears to depend on being able to fit in to the dominant masculine culture of long working hours and the male pub gathering. Despite an increased presence, women's minority status in construction continues to challenge their professional identity and this is central to the conflict many face between the dual roles of corporate worker and private non‐work person.