Sample size considerations using mathematical models: an example with Chlamydia trachomatis infection and its sequelae pelvic inflammatory disease.

BACKGROUND The success of an intervention to prevent the complications of an infection is influenced by the natural history of the infection. Assumptions about the temporal relationship between infection and the development of sequelae can affect the predicted effect size of an intervention and the sample size calculation. This study investigates how a mathematical model can be used to inform sample size calculations for a randomised controlled trial (RCT) using the example of Chlamydia trachomatis infection and pelvic inflammatory disease (PID). METHODS We used a compartmental model to imitate the structure of a published RCT. We considered three different processes for the timing of PID development, in relation to the initial C. trachomatis infection: immediate, constant throughout, or at the end of the infectious period. For each process we assumed that, of all women infected, the same fraction would develop PID in the absence of an intervention. We examined two sets of assumptions used to calculate the sample size in a published RCT that investigated the effect of chlamydia screening on PID incidence. We also investigated the influence of the natural history parameters of chlamydia on the required sample size. RESULTS The assumed event rates and effect sizes used for the sample size calculation implicitly determined the temporal relationship between chlamydia infection and PID in the model. Even small changes in the assumed PID incidence and relative risk (RR) led to considerable differences in the hypothesised mechanism of PID development. The RR and the sample size needed per group also depend on the natural history parameters of chlamydia. CONCLUSIONS Mathematical modelling helps to understand the temporal relationship between an infection and its sequelae and can show how uncertainties about natural history parameters affect sample size calculations when planning a RCT.

Building up and sharing knowledge for better decision making on soil and water conservation in a changing mountain environment - the WOCAT experience

For successful implementation of any soil and water conservation (SWC) or sustainable land management practice, it is essential to have a proper understanding of the natural and human environment in which these practices are applied. This understanding should be based on comprehensive information concerning the application of the technologies and not solely on the technological details. The World Overview of Conservation Approaches and Technologies (WOCAT) is documenting and evaluating SWC practices worldwide, following a standardised methodology that facilitates exchange and comparison of experiences. Notwithstanding this standardisation, WOCAT allows flexible use of its outputs, adapted to different users and different environments. WOCAT offers a valuable tool for evaluating the strengths and weaknesses of SWC practices and their potential for application in other areas. Besides collecting a wealth of information, gaps in available information are also exposed, showing the need for more research in those fields. Several key issues for development- oriented research have been identified and are being addressed in collaboration with a research programme for mitigating syndromes of global change.

Perceptual Training in Beach Volleyball Defence: Different Effects of Gaze-Path Cueing on Gaze and Decision-Making

For perceptual-cognitive skill training, a variety of intervention methods has been proposed, including the so-called “color-cueing method” which aims on superior gaze-path learning by applying visual markers. However, recent findings challenge this method, especially, with regards to its actual effects on gaze behavior. Consequently, after a preparatory study on the identification of appropriate visual cues for life-size displays, a perceptual-training experiment on decision-making in beach volleyball was conducted, contrasting two cueing interventions (functional vs. dysfunctional gaze path) with a conservative control condition (anticipation-related instructions). Gaze analyses revealed learning effects for the dysfunctional group only. Regarding decision-making, all groups showed enhanced performance with largest improvements for the control group followed by the functional and the dysfunctional group. Hence, the results confirm cueing effects on gaze behavior, but they also question its benefit for enhancing decision-making. However, before completely denying the method’s value, optimisations should be checked regarding, for instance, cueing-pattern characteristics and gaze-related feedback.

Soil and land information: How to support decision-making?

Soils are fundamental to ensuring water, energy and food security. Within the context of sus- tainable food production, it is important to share knowledge on existing and emerging tech- nologies that support land and soil monitoring. Technologies, such as remote sensing, mobile soil testing, and digital soil mapping, have the potential to identify degraded and non- /little-responsive soils, and may also provide a basis for programmes targeting the protection and rehabilitation of soils. In the absence of such information, crop production assessments are often not based on the spatio-temporal variability in soil characteristics. In addition, uncertain- ties in soil information systems are notable and build up when predictions are used for monitor- ing soil properties or biophysical modelling. Consequently, interpretations of model-based results have to be done cautiously. As such they provide a scientific, but not always manage- able, basis for farmers and/or policymakers. In general, the key incentives for stakeholders to aim for sustainable management of soils and more resilient food systems are complex at farm as well as higher levels. The same is true of drivers of soil degradation. The decision- making process aimed at sustainable soil management, be that at farm or higher level, also in- volves other goals and objectives valued by stakeholders, e.g. land governance, improved envi- ronmental quality, climate change adaptation and mitigation etc. In this dialogue session we will share ideas on recent developments in the discourse on soils, their functions and the role of soil and land information in enhancing food system resilience.

Using technology to enhance decision making

We focus here on decision making in the everyday clinical situation and do not address decision making in politics and administration, although obviously it affects clinical practice and vice versa. For example, decisions against providing sufficient face-to-face psychotherapy is one factor that may increase the demand for Internet therapy, and vice versa—that is, the use of technology for therapy, as in Internet therapy, might influence to what extent face-to-face therapy needs to be provided. It is obvious that the aggregation of information for political and administrative decisions can take advantage of technology. If technology is used professionally, this should contribute to better informed decisions and less dependency on information provided by lobbyists who might not work in the interest of high-quality service for those who need it. An optimistic view is thus that technology works in favor of patients on this level as well. In the interest of keeping the focus of this chapter manageable, we also do not address treatments fully delivered over the Internet or computers, as for the example described in Comer and Barlow (2014), although such treatments, as they unfold, of course also include decision making.

Emotions, Not Just Decision-Making Processes, Are Critical to an Evolutionary Model of Human Behavior

An evolutionary model of human behavior should privilege emotions: essential, phylogenetically ancient behaviors that learning and decision making only subserve. Infants and non-mammals lack advanced cognitive powers but still survive. Decision making is only a means to emotional ends, which organize and prioritize behavior. The emotion of pride/shame, or dominance striving, bridges the social and biological sciences via internalization of cultural norms.

Family Court Judges' Training, Background, and Child Development Knowledge: Associations with Child Custody Decision Making

Family court judges are often asked to make inferences about - or directly interview children to ascertain - children's custody preferences and their maturity to express such preferences. These estimates of children's developmental maturity are important to the judges' considerations of children's "best interests" in custody cases. The research literature describing family court judges' background, education, training, and knowledge about child development is scant. With appropriate child development knowledge, judges should be better able to identify the developmental stages at which children have the cognitive and social capabilities to communicate directly their placement wishes or concerns. The current study is the first to examine judges' estimates of - and actual tests of - their child development knowledge, their training/education, and their application of this knowledge to their decisions to involve children as participants in contested custody cases.

Grief, Physical Symptoms, and Decision-Making in Mothers of Newborns Who Die

The purpose of this study was to describe predictors of level of grief and physical symptoms in mothers during the year after a newborn death. This was undertaken to fmd better ways to help these mothers during this crisis. Following appropriate approvals, volunteer subjects were contacted through hospitals, the Internet, and a health department. Of the 75 who responded, 77% were White and married, 64% were Christian. 51 % had other living children, 72% had had no prior pregnancy losses, 87% had support with decision-making about newborn care, and their mean age was 30 yrs. Once subjects had agreed to take Par4 the survey and consent form were sent to them. Study outcome variables were: Total scores on the Perinatal Grief Scale, Short Version (level of grief; T oedter, Lasker, & Alhadeff. 1988) and Sickness Impact Profile 68 (level of physical symptoms; de Bruin, Buys, de Witte, & Diederiks, 1994). Predictor variables were total scores on the Personal Resources Questionnaire 85, Part U (perceived support; Brandt & Weinert, 1981); Relationship Satisfaction Questionnaire (relationship satisfaction; Olson & McCubbin, 1983); Emotion-Focused. Problem-Focused, and Mixed Coping Subscales (emotion-focused, problem-focused, and mixed coping; Lazarus & Folkman, 1988); interval since death, ethnicity, religion, socioeconomic status, gestational age, and presence of living children. Coefficient alphas for scales were all over .75. In two stepwise-hierarchical multiple regressions, perceived support and emotion- focused coping combined to predict 43% of the variance in level of grief, and level of grief alone predicted 50% of the variance in level of physical symptoms. In written comments, mothers said they valued their role in decision-making about newborn care even with death as the result. and felt supported in that process. Findings may be used to design intervention programs to help bereaved mothers following a newborn death. Specifically, programs can help increase perceived support for bereaved mothers, and teach new ways of coping. Both strategies may result in lower levels of grief and physical symptoms in this group of bereaved mothers.

A Qualitative Study of the Assistive Technology Decision-Making Process in Four Pennsylvania School Districts

The purpose of this study was to gain an understanding of the Assistive Technology decision making process at four regional school districts in Pennsylvania. A qualitative case study research method involving the triangulation of data sources was implemented to collect and analyze data. Through an analysis of the data, three major topics emerged that will be addressed in the body of this paper: (a) the procedure for determining assistive technology needs and the dynamics of the decision-making process, b) the cohesiveness of Special Education and General Education programs, and c) major concerns that impact the delivery of assistive technology services.

The Devil’s Calculus: Mathematical Models of Civil War

In spite of the movement to turn political science into a real science, various mathematical methods that are now the staples of physics, biology, and even economics are thoroughly uncommon in political science, especially the study of civil war. This study seeks to apply such methods - specifically, ordinary differential equations (ODEs) - to model civil war based on what one might dub the capabilities school of thought, which roughly states that civil wars end only when one side’s ability to make war falls far enough to make peace truly attractive. I construct several different ODE-based models and then test them all to see which best predicts the instantaneous capabilities of both sides of the Sri Lankan civil war in the period from 1990 to 1994 given parameters and initial conditions. The model that the tests declare most accurate gives very accurate predictions of state military capabilities and reasonable short term predictions of cumulative deaths. Analysis of the model reveals the scale of the importance of rebel finances to the sustainability of insurgency, most notably that the number of troops required to put down the Tamil Tigers is reduced by nearly a full order of magnitude when Tiger foreign funding is stopped. The study thus demonstrates that accurate foresight may come of relatively simple dynamical models, and implies the great potential of advanced and currently unconventional non-statistical mathematical methods in political science.