Locally and maximin optimal designs for multi-factor nonlinear models

This paper considers the search for locally and maximin optimal designs for multi-factor nonlinear models from optimal designs for sub-models of a lower dimension. In particular, sufficient conditions are given so that maximin D-optimal designs for additive multi-factor nonlinear models can be built from maximin D-optimal designs for their sub-models with a single factor. Some examples of application are models involving exponential decay in several variables.     

A Cox‐Aalen Model for Interval‐censored Data

The Cox‐Aalen model, obtained by replacing the baseline hazard function in the well‐known Cox model with a covariate‐dependent Aalen model, allows for both fixed and dynamic covariate effects. In this paper, we examine maximum likelihood estimation for a Cox‐Aalen model based on interval‐censored failure times with fixed covariates. The resulting estimator globally converges to the truth slower than the parametric rate, but its finite‐dimensional component is asymptotically efficient. Numerical studies show that estimation via a constrained Newton method performs well in terms of both finite sample properties and processing time for moderate‐to‐large samples with few covariates. We conclude with an application of the proposed methods to assess risk factors for disease progression in psoriatic arthritis.     

Why Competition from a Multi‐Channel E‐Tailer Does Not Always Benefit Consumers*

Empirical studies have delivered mixed conclusions on whether the widely acclaimed assertions of lower electronic retail (e‐tail) prices are true and to what extent these prices impact conventional retail prices, profits, and consumer welfare. For goods that require little in‐person pre‐ or postsales support such as CDs, DVDs, and books, we extend Balasubramanian's e‐tailer‐in‐the‐center, spatial, circular market model to examine the impact of a multichannel e‐tailer's presence on retailers' decisions to relocate, on retail prices and profits, and consumer welfare. We demonstrate several counter‐intuitive results. For example, when the disutility of buying online and shipping costs are relatively low, retailers are better off by not relocating in response to an e‐tailer's entry into the retail channel. In addition, such an entry—a multichannel strategy—may lead to increased retail prices and increased profits across the industry. Finally, consumers can be better off with less channel competition. The underlying message is that inferences regarding prices, profits, and consumer welfare critically depend on specifications of the good, disutility and shipping costs versus transportation costs (or more generally, positioning), and competition.     

The Recalled Childhood Gender Questionnaire-Revised: a psychometric analysis in a sample of women with congenital adrenal hyperplasia

We administered the 18-item Recalled Childhood Gender Questionnaire-Revised (RCGQ-R), female version, to 147 adult women with congenital adrenal hyperplasia (CAH) representing three different degrees of prenatal androgenization due to 21-hydroxylase deficiency and to non-CAH controls. A principal components analysis generated three components accounting for 46%, 9%, and 6% of the variance, respectively. Corresponding unit-weighted scales (high scores = feminine) were labeled Gender Role (13 items; Cronbach alpha = .91), Physical Activity (3 items; alpha = .64), and Cross-Gender Desire (2 items; alpha = .47). Discriminant validity was demonstrated in terms of highly significant comparisons across the four groups. We conclude that the first 2 RCGQ-R scales show good psychometric qualities, but that the third scale needs to be further evaluated in a sample that includes women with gender identity disorder.     

Virtual journey coupled with face‐to‐face exchange: enhancing the cultural sensitivity and competence of graduate students

This study attempted to enhance cultural sensitivity for graduate students at an American and a South African university, using a six‐week online List Serv, email buddy exchange, and two‐week face‐to‐face experience. After the course was over, results of the intercultural developmental inventory, using t‐tests for related samples, showed that there was a significant difference (alpha equals .04) in the universalism and cognitive frame shifting clusters as well as the overall developmental cultural level of sensitivity. Positive trends were noted in the areas of cultural self‐identity enhancement, and a decrease in inflation in the area of perceived intercultural sensitivity was noted.     

Sex and Gender Diversity Among Transgender Persons in Ontario,Canada: Results From a Respondent-Driven Sampling Survey

Recent estimates suggest that as many as 1 in 200 adults may be trans (transgender, transsexual, or transitioned). Knowledge about dimensions of sex and gender in trans populations is crucial to development of inclusive policy, practice, and research, but limited data have been available, particularly from probability samples. The Trans PULSE community-based research project surveyed trans Ontarians (n = 433) in 2009–2010 using respondent-driven sampling. Frequencies were weighted by recruitment probability to produce estimates for the networked Ontario trans population. An estimated 30% of trans Ontarians were living their day-to-day lives in their birth gender, and 23% were living in their felt gender with no medical intervention. In all, 42% were using hormones, while 15% of male-to-female spectrum persons had undergone vaginoplasty and 0.4% of female-to-male spectrum persons had had phalloplasty. Of those living in their felt gender, 59% had begun to do so within the past four years. A minority of trans Ontarians reported a linear transition from one sex to another, yet such a trajectory is often assumed to be the norm. Accounting for this observed diversity, we recommend policy and practice changes to increase social inclusion and service access for trans persons, regardless of transition status.     

Enhancing response rates to a smoking survey for enlisted U.S. Navy women.

This study examined the effectiveness of a stepped approach for increasing response rates to a mailed follow-up smoking survey among newly enlisted women in the navy. The effect of the stepped approach on response rates and on the characteristics of respondents was evaluated. Also, costs were estimated for each of the steps to determine their relative benefits. Results showed that the stepped approach was effective in more than doubling the survey response rate among smokers. Reluctant respondents did not differ from on-time respondents in terms of demographics or baseline smoking, although nonrespondents were less educated and heavier smokers than on-time and reluctant respondents. Strategies documented here could well apply to survey efforts with other hard-to-reach populations.     

Cue-Reactive Rationality,Visual Imagery and Volitional Control Predict Cue-Reactive Urge to Gamble in Poker-Machine Gamblers

Poker-machine gamblers have been demonstrated to report increases in the urge to gamble following exposure to salient gambling cues. However, the processes which contribute to this urge to gamble remain to be understood. The present study aimed to investigate whether changes in the conscious experience of visual imagery, rationality and volitional control (over one’s thoughts, images and attention) predicted changes in the urge to gamble following exposure to a gambling cue. Thirty-one regular poker-machine gamblers who reported at least low levels of problem gambling on the Problem Gambling Severity Index (PGSI), were recruited to complete an online cue-reactivity experiment. Participants completed the PGSI, the visual imagery, rationality and volitional control subscales of the Phenomenology of Consciousness Inventory (PCI), and a visual analogue scale (VAS) assessing urge to gamble. Participants completed the PCI subscales and VAS at baseline, following a neutral video cue and following a gambling video cue. Urge to gamble was found to significantly increase from neutral cue to gambling cue (while controlling for baseline urge) and this increase was predicted by PGSI score. After accounting for the effects of problem-gambling severity, cue-reactive visual imagery, rationality and volitional control significantly improved the prediction of cue-reactive urge to gamble. The small sample size and limited participant characteristic data restricts the generalizability of the findings. Nevertheless, this is the first study to demonstrate that changes in the subjective experience of visual imagery, volitional control and rationality predict changes in the urge to gamble from neutral to gambling cue. The results suggest that visual imagery, rationality and volitional control may play an important role in the experience of the urge to gamble in poker-machine gamblers.