High-dimensional changepoint detection via a geometrically inspired mapping

Statistics and Computing - High-dimensional changepoint analysis is a growing area of research and has applications in a wide range of fields. The aim is to accurately and efficiently detect...     

Evaluating the Temporal Location of Feedback: Providing Feedback Following Performance vs. Prior to Performance

In order to make feedback as effective as possible, it is important to understand its function in the three-term contingency (TTC) and the impact of various factors involved in delivering feedback. Timing of feedback is one factor that can affect the impact of feedback on learner’s behavior. An analysis of timing of feeback may help us getting closer to better understanding how feedback functions in the TTC. The purpose of this study was to evaluate the effects of feedback at different temporal locations. Specifically, feedback was provided either immediately (a) after a teaching session or (b) before the following teaching session, on teaching performance of undergraduate psychology students. The results indicated that feedback provided before the teaching session was more effective in improving teaching skills than feedback that was provided after the session. These findings suggest that feedback may function primarily as an antecedent to future performance and not necessarily as a consequence for past performance. However, the behavioral mechanism that explains these results is not yet clear. Future studies should investigate this further by manipulating the content of feedback prior to the teaching performance.     

Embeddedness of Organizational Capabilities*

Managers must regularly make decisions on how to access and deploy their limited resources in order to build organizational capabilities for a sustainable competitive advantage. However, failure to recognize that organizational capabilities involve complex and intricately woven underlying processes may lead to an incomplete understanding of how capabilities affect competitive advantage. As a means of understanding this underlying complexity, we discuss how managerial decisions on resource acquisition and deployment influence capability embeddedness and argue that capability embeddedness has an incremental effect on firm performance beyond the effects from organizational resources and capabilities. To investigate these issues, we present a hierarchical composed error structure framework that relies on cross‐sectional data (and allows for generalizations to panel data). We demonstrate the framework in the context of retailing, where we show that the embeddedness of organizational capabilities influences retailer performance above and beyond the tangible and intangible resources and capabilities that a retailer possesses. Our results illustrate that understanding how resources and capabilities influence performance at different hierarchical levels within a firm can aid managers to make better decisions on how they can embed certain capabilities within the structural and social relationships within the firm. Moreover, understanding whether the underlying objectives of the capabilities that are being built and cultivated have convergent or divergent goals is critical, as it can influence the extent to which the embedded capabilities enhance firm performance.     

Risk of Legionellosis in residential areas around farms irrigating with municipal wastewater

The conservation of freshwater is of both global and national importance, and in the United States, agriculture is one of the largest consumers of this resource. Reduction of the strain farming puts on local surface or groundwater is vital for ensuring resilience in the face of climate change, and one possible option is to irrigate with a combination of freshwater and reclaimed water from municipal wastewater treatment facilities. However, this wastewater can contain pathogens that are harmful to human health, such as Legionella pneumophila, which is a bacterium that can survive aerosolization and airborne transportation and cause severe pneumonia when inhaled. To assess an individual adult's risk of infection with L. pneumophila from a single exposure to agricultural spray irrigation, a quantitative microbial risk assessment was conducted for a scenario of spray irrigation in central Illinois, for the growing seasons in 2017, 2018, and 2019. The assessment found that the mean risk of infection for a single exposure exceeded the safety threshold of 10^–6 infections/exposure up to 1 km from a low-pressure irrigator and up to 2 km from a high-pressure irrigator, although no median risk exceeded the threshold for any distance or irrigator pressure. These findings suggest that spray irrigation with treated municipal wastewater could be a viable option for reducing freshwater consumption in Midwest farming, as long as irrigation on windy days is avoided and close proximity to the active irrigator is limited.     

Effects of unmeasured heterogeneity in the linear transformation model for censored data

We investigate the effect of unobserved heterogeneity in the context of the linear transformation model for censored survival data in the clinical trials setting. The unobserved heterogeneity is represented by a frailty term, with unknown distribution, in the linear transformation model. The bias of the estimate under the assumption of no unobserved heterogeneity when it truly is present is obtained. We also derive the asymptotic relative efficiency of the estimate of treatment effect under the incorrect assumption of no unobserved heterogeneity. Additionally we investigate the loss of power for clinical trials that are designed assuming the model without frailty when, in fact, the model with frailty is true. Numerical studies under a proportional odds model show that the loss of efficiency and the loss of power can be substantial when the heterogeneity, as embodied by a frailty, is ignored. An erratum to this article can be found at     

A computationally simple bivariate survival estimator for efficacy and safety

Both treatment efficacy and safety are typically the primary endpoints in Phase II, and even in some Phase III, clinical trials. Efficacy is frequently measured by time to response, death, or some other milestone event and thus is a continuous, possibly censored, outcome. Safety, however, is frequently measured on a discrete scale; in Eastern Cooperative Oncology Group clinical trial E2290, it was measured as the number of weekly rounds of chemotherapy that were tolerable to colorectal cancer patients. For the joint analysis of efficacy and safety, we propose a non-parametric, computationally simple estimator for the bivariate survival function when one time-to-event is continuous, one is discrete, and both are subject to right-censoring. The bivariate censoring times may depend on each other, but they are assumed to be independent of both event times. We derive a closed-form covariance estimator for the survivor function which allows for inference to be based on any of several possible statistics of interest. In addition, we derive its covariance with respect to calendar time of analysis, allowing for its use in sequential studies.     

Subjective Versus Objective Definitions of Homelessness: Are there Differences in Risk Factors among Heavy-Drinking Women?

Investigations with homeless populations have focused on those living on the streets or in shelters; few have examined phenomena based on respondents’ self-definitions as homeless or not. This investigation examined similarities and differences among risk factors (including mental health, substance abuse, religion/spirituality, social support, and risky sexual behaviors) using two definitions of homelessness: one where place of residence defined individuals as homeless (the ‘objective’ or traditional, definition) and another where respondents defined themselves as homeless (the ‘subjective’ definition). Data come from the baseline survey of the NIAAA-funded “Sister-to-Sister” study (n = 339) of heavy-drinking women. Subjectively defined homelessness was associated with higher rates of mental health and substance use disorders, lower rates of condom use, higher rates of trading sex for food, and less social support. Objectively defined homelessness was associated with higher rates of drinking in abandoned buildings, on the streets, and in public restrooms, more new sexual partners, and higher rates of trading sex for heroin and speedballs. Investigations failing to ask for subjective information may misattribute some factors to homelessness which may overestimate the effect of various factors on homelessness. Investigators should ask respondents to define their homelessness, or they lose an important dimension of the concept of homelessness.

Substance use and vulnerability to sexual and physical aggression: a longitudinal study of young adults

Using data from 2,170 individuals who participated in Waves 8 (age 23) and 9 (age 29) of a multiyear panel study, this study examined whether alcohol and marijuana use in young adulthood increase one's risk for experiencing subsequent sexual or physical assault victimization, whether victims' own violent behavior or involvement in the sale of drugs explain any effects of substance use on victimization, and whether these associations differ by gender. Controlling for prior victimization, we found that marijuana use, but not alcohol use, predicted women's and men's subsequent sexual victimization and men's subsequent physical assault victimization, and that heavy alcohol use, but not marijuana use, predicted women's subsequent physical assault victimization. Whereas the links from marijuana use to victimization were explained by users' own violent behavior, the link from alcohol use to women's physical assault victimization was not.