Variance reduction in randomised trials by inverse probability weighting using the propensity score.

In individually randomised controlled trials, adjustment for baseline characteristics is often undertaken to increase precision of the treatment effect estimate. This is usually performed using covariate adjustment in outcome regression models. An alternative method of adjustment is to use inverse probability-of-treatment weighting (IPTW), on the basis of estimated propensity scores. We calculate the large-sample marginal variance of IPTW estimators of the mean difference for continuous outcomes, and risk difference, risk ratio or odds ratio for binary outcomes. We show that IPTW adjustment always increases the precision of the treatment effect estimate. For continuous outcomes, we demonstrate that the IPTW estimator has the same large-sample marginal variance as the standard analysis of covariance estimator. However, ignoring the estimation of the propensity score in the calculation of the variance leads to the erroneous conclusion that the IPTW treatment effect estimator has the same variance as an unadjusted estimator; thus, it is important to use a variance estimator that correctly takes into account the estimation of the propensity score. The IPTW approach has particular advantages when estimating risk differences or risk ratios. In this case, non-convergence of covariate-adjusted outcome regression models frequently occurs. Such problems can be circumvented by using the IPTW adjustment approach

Harmonizing the Policy of the Bankruptcy Code and Article 9

In a true sense bankruptcy law--at least as represented by the 1978 Code--is in conflict, not in harmony, with Article 9. To a considerable degree (perhaps more than they realize) debtors and unsecured creditors got things they wanted from Congress by the adoption of the Bankruptcy Reform Act of 1978. It is doubtful that that Act could have been passed in any Congress before or since. In many ways, the rights of the debtor and of the unsecured creditors have been cut back since the adoption of the Bankruptcy Reform Act

Harmonizing the Policy of the Bankruptcy Code and Article 9

In a true sense bankruptcy law--at least as represented by the 1978 Code--is in conflict, not in harmony, with Article 9. To a considerable degree (perhaps more than they realize) debtors and unsecured creditors got things they wanted from Congress by the adoption of the Bankruptcy Reform Act of 1978. It is doubtful that that Act could have been passed in any Congress before or since. In many ways, the rights of the debtor and of the unsecured creditors have been cut back since the adoption of the Bankruptcy Reform Act

The Developement of an Educational Program in Iowa State Parks

The first state park was created in 1918; consequently the state park educational program is of recent development. Although the educational program and the development of a park system by the state is relatively new, the idea of state-owned lands for recreational purposes is almost as old as our statehood. T. S. Parvin, registrar of lands back in the fifties, advocated in one of his reports that the state should buy a large tract of land in Des Moines to preserve the statehouse ground, for in time the state would need it for recreational purposes. It is evident now that Parvin was at least a half century ahead of his time, because the act providing for the establishment of state parks was passed by the Thirty-seventh General Assembly in 1917

Form Follows Function: Adapting the Strength Model to Facilitate Implementation and Sustainability

Case management is a common social service intervention that has been applied across a range of disciplines, populations, and types of organizations. Despite its widespread use, the activities constituting case management are often poorly specified (Lukersmith, Millington, & Salvador-Carulla, 2016). The Strengths Model is an important exception—not only does it offer a structured approach to service delivery, but it provides enough flexibility to facilitate implementation and support sustainability. The goal of this chapter is to help practitioners think creatively about implementation, so they can meet the needs of their organization while remaining true to the core components of the Strengths Model. In the first part of this chapter, we discuss the delicate balance between implementing a model to fidelity and mak- ing adaptations to address organizational barriers and constraints, highlighting some of the prior modifications made to the Strengths Model to ease implementation. In the second part of the chapter, we describe one agency’s approach to implementa- tion, the structural adaptations staff made to the Strengths Model, and the benefits and challenges associated with their approach

Artemisinin resistance--modelling the potential human and economic costs.

BACKGROUND: Artemisinin combination therapy is recommended as first-line treatment for falciparum malaria across the endemic world and is increasingly relied upon for treating vivax malaria where chloroquine is failing. Artemisinin resistance was first detected in western Cambodia in 2007, and is now confirmed in the Greater Mekong region, raising the spectre of a malaria resurgence that could undo a decade of progress in control, and threaten the feasibility of elimination. The magnitude of this threat has not been quantified. METHODS: This analysis compares the health and economic consequences of two future scenarios occurring once artemisinin-based treatments are available with high coverage. In the first scenario, artemisinin combination therapy (ACT) is largely effective in the management of uncomplicated malaria and severe malaria is treated with artesunate, while in the second scenario ACT are failing at a rate of 30%, and treatment of severe malaria reverts to quinine. The model is applied to all malaria-endemic countries using their specific estimates for malaria incidence, transmission intensity and GDP. The model describes the direct medical costs for repeated diagnosis and retreatment of clinical failures as well as admission costs for severe malaria. For productivity losses, the conservative friction costing method is used, which assumes a limited economic impact for individuals that are no longer economically active until they are replaced from the unemployment pool. RESULTS: Using conservative assumptions and parameter estimates, the model projects an excess of 116,000 deaths annually in the scenario of widespread artemisinin resistance. The predicted medical costs for retreatment of clinical failures and for management of severe malaria exceed US$32 million per year. Productivity losses resulting from excess morbidity and mortality were estimated at US$385 million for each year during which failing ACT remained in use as first-line treatment. CONCLUSIONS: These 'ballpark' figures for the magnitude of the health and economic threat posed by artemisinin resistance add weight to the call for urgent action to detect the emergence of resistance as early as possible and contain its spread from known locations in the Mekong region to elsewhere in the endemic world

Semileptonic BcB_c Decay and Heavy Quark Spin Symmetry

Semileptonic decay of the $B_c$ meson is studied in the heavy quark limit. The six possible form factors for $B_c \rightarrow B_s (B^0),B_s^* (B^{*0})$ semileptonic decay are determined by two invariant functions. Only one of these functions contributes at zero recoil, where it is calculable to lowest order in an operator product expansion in terms of the meson decay constant $f_B$ and the $B_c$ wavefunction. A similar result is found for $B_c \rightarrow D^0,D^{*0}$ and for $B_c\rightarrow\eta_c,J/\psi$ semileptonic decay for a restricted kinematic region. Semileptonic $B_c$ decay provides a means for determining the KM mixing angle $|V_{ub}|$.Comment: (12 Pages, no figures

Planning a method for covariate adjustment in individually randomised trials: a practical guide

Background: It has long been advised to account for baseline covariates in the analysis of confirmatory randomised trials, with the main statistical justifications being that this increases power and, when a randomisation scheme balanced covariates, permits a valid estimate of experimental error. There are various methods available to account for covariates but it is not clear how to choose among them. // Methods: Taking the perspective of writing a statistical analysis plan, we consider how to choose between the three most promising broad approaches: direct adjustment, standardisation and inverse-probability-of-treatment weighting. // Results: The three approaches are similar in being asymptotically efficient, in losing efficiency with mis-specified covariate functions and in handling designed balance. If a marginal estimand is targeted (for example, a risk difference or survival difference), then direct adjustment should be avoided because it involves fitting non-standard models that are subject to convergence issues. Convergence is most likely with IPTW. Robust standard errors used by IPTW are anti-conservative at small sample sizes. All approaches can use similar methods to handle missing covariate data. With missing outcome data, each method has its own way to estimate a treatment effect in the all-randomised population. We illustrate some issues in a reanalysis of GetTested, a randomised trial designed to assess the effectiveness of an electonic sexually transmitted infection testing and results service. // Conclusions: No single approach is always best: the choice will depend on the trial context. We encourage trialists to consider all three methods more routinely

Extracting Information from Adaptive Control Experiments

Optical control of chemical reactivity is achieved through the use of photonic reagents, that is, “shaped” ultrafast optical pulses created using a pulse shaper. It has been demonstrated in a number of molecular systems that these pulses can effectively guide the system into a desired final state. Effective pulses are often found through an experimental search involving thousands of individual measurements. An examination of the pulses tested in these experiments can reveal the pulse features responsible for control and also the underlying molecular dynamics. In this article we review attempts to extract information from optical control experiments using adaptive learning algorithms to search the available parameter space, and we discuss how these kinds of experiments can be used to achieve and understand multiphoton optical control.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91361/1/397_ftp.pd