A stochastically curtailed two-arm randomised phase II trial design for binary outcomes

Randomised controlled trials are considered the gold standard in trial design. However, phase II oncology trials with a binary outcome are often single-arm. Although a number of reasons exist for choosing a single-arm trial, the primary reason is that single-arm designs require fewer participants than their randomised equivalents. Therefore, the development of novel methodology that makes randomised designs more efficient is of value to the trials community. This article introduces a randomised two-arm binary outcome trial design that includes stochastic curtailment (SC), allowing for the possibility of stopping a trial before the final conclusions are known with certainty. In addition to SC, the proposed design involves the use of a randomised block design, which allows investigators to control the number of interim analyses. This approach is compared with existing designs that also use early stopping, through the use of a loss function comprised of a weighted sum of design characteristics. Comparisons are also made using an example from a real trial. The comparisons show that for many possible loss functions, the proposed design is superior to existing designs. Further, the proposed design may be more practical, by allowing a flexible number of interim analyses. One existing design produces superior design realisations when the anticipated response rate is low. However, when using this design, the probability of rejecting the null hypothesis is sensitive to misspecification of the null response rate. Therefore, when considering randomised designs in phase II, we recommend the proposed approach be preferred over other sequential designs.     

Optimal classification scores based on multivariate marker transformations

AStA Advances in Statistical Analysis - Modern science frequently involves the study of complex relationships among effects and factors. Flexible statistical tools are commonly used to visualize...     

Unwanted sexual experiences and sexual risks in gay and bisexual men: Associations among revictimization,substance use,and psychiatric symptoms

The data set of 2,182 gay/bisexual men's month‐long sexual diaries collected by the United Kingdom Socio‐sexual Investigations of Gay Men and Aids (Project SIGMA) was used to analyse the extent to which acts of anal intercourse (AI) are distributed among gay men, using the Lorenz/Gini methodology for measuring concentration. Most individuals (60%) who engage in AI do so only once or twice a month, but there is a long tail of those who do it much more. In terms of the amount of AI acts, one tenth of the individuals are performing half of the acts of AI. The Gini coefficient of concentration is high (0.55). Factors most affecting rates and concentration of risk behaviour include relationship status, HIV sero‐status and concordant/discordant partner status.     

An examination of sexual strategies used by urban southern and rural Midwestern university women

The purposes of this study were (a) to determine whether women's use of persuasion, non‐physical coercion, and physical force strategies to obtain sex from a man varied between U.S. women from an urban Southern and rural Midwestern university and (b) to determine if sexual behavior history and early courtship behavior affected the use of these strategies (or not using any strategy). Women from the Midwest and the South did not differ in their use of sexual strategies. There were, however, other variables that accounted for differences in women's use of sexual strategies. Women who used persuasion strategies had fewer lifetime sexual partners than women who used any other strategy. Women who used physical force strategies reported a lower age at first intercourse and more early courtship behaviors than all others. Overall, the results indicated that sexual strategies are related to sexual behavior history and early courtship behaviors rather than cultural setting or demographics.     

The ambiguity of “having sex”: The subjective experience of virginity loss in the united states

Ambiguity surrounds virginity loss as defined and interpreted by young people in the contemporary United States. Drawing on in‐depth case studies of 61 women and men of various sexual orientations, ages 18 to 35, I explore the influence of that ambiguity on conduct and identity. Although uniformly agreeing that virginity loss could occur through first coitus, most respondents claimed that other kinds of genital sex could also sometimes result in virginity loss. Many argued that virginity could not be lost through rape. Respondents offered three primary interpretations of virginity—as a gift, stigma, or part of a process—which were associated with distinctive presentations of self, choices of virginity‐loss partner, and contraceptive practices. Different definitions and interpretations of virginity loss gave distinctive shape to individuals ‘ choices about the transitions from virgin to nonvirgin identity. Understandings of virginity loss were further patterned by gender and sexual orientation.     

Evaluation of two school‐based HIV prevention interventions in the border city of Tijuana,Mexico

This research project examined the individual and combined effectiveness of an HIV prevention workshop and a free condom distribution program in four high schools in Tijuana, Mexico. Adolescents (N = 320) completed baseline measures on sexual practices and theoretical correlates and participated in a two‐part study. In Study I, students were randomly assigned to an HIV prevention workshop or a control condition, with a 3‐month follow‐up assessment. Results indicate three significant workshop benefits regarding HIV transmission by altering sexual initiation, access to condoms, and traditional beliefs regarding condoms. In Study 2, we set up a condom distribution program at two of the participating schools, and students completed a 6‐month follow‐up assessment. Results indicate that exposure to the workshop followed by access to the condom distribution program yielded two beneficial results for reducing HIV transmission: moderating sexual initiation and increasing condom acquisition. Access to the condom distribution program alone had no effects on behavioral and psy‐chosocial correlates of HFV transmission. We discuss implications of these results.