Optimal designs for the development of personalized treatment rules

We study the design of multi-armed parallel group clinical trials to estimate personalized treatment rules that identify the best treatment for a given patient with given covariates. Assuming that the outcomes in each treatment arm are given by a homoscedastic linear model, with possibly different variances between treatment arms, and that the trial subjects form a random sample from an unselected overall population, we optimize the (possibly randomized) treatment allocation allowing the allocation rates to depend on the covariates. We find that, for the case of two treatments, the approximately optimal allocation rule does not depend on the value of the covariates but only on the variances of the responses. In contrast, for the case of three treatments or more, the optimal treatment allocation does depend on the values of the covariates as well as the true regression coefficients. The methods are illustrated with a recently published dietary clinical trial.     

Better experimental design by hybridizing binary matching with imbalance optimization

We present a new experimental design procedure that divides a set of experimental units into two groups in order to minimize error in estimating a treatment effect. One concern is the elimination of large covariate imbalance between the two groups before the experiment begins. Another concern is robustness of the design to misspecification in response models. We address both concerns in our proposed design: we first place subjects into pairs using optimal nonbipartite matching, making our estimator robust to complicated nonlinear response models. Our innovation is to keep the matched pairs extant, take differences of the covariate values within each matched pair, and then use the greedy switching heuristic of Krieger et al. (2019) or rerandomization on these differences. This latter step greatly reduces covariate imbalance. Furthermore, our resultant designs are shown to be nearly as random as matching, which is robust to unobserved covariates. When compared to previous designs, our approach exhibits significant improvement in the mean squared error of the treatment effect estimator when the response model is nonlinear and performs at least as well when the response model is linear. Our design procedure can be found as a method in the open source R package available on CRAN called GreedyExperimentalDesign .     

Some thoughts about image modeling

There is an extensive literature on image models; perhaps the greatest emphasis has been on models based on Markov random fields. This article briefly discusses some general aspects of image modeling:what should be modeled (the scene rather than the image; both the ‘objects' and the ‘clutter’); the importance of non-standard types of models; the oversimplification of conventional models; possible limitations on the effectiveness of realistic models; models in higher-dimensional domains; and general guidelines for selecting problems to which models can be effectively applied.     

Be Happy Because Your Father Isn't Your Father: An Analysis of Colombian Telenovelas

Critics of mass-mediated culture have long maintained that media such as television, radio, and newspapers are instrumental in propagating class values. In his analysis of Colombian telenovelas, Azriel Bibliowicz argues that this apparently harmless form of entertainment also has a political and ideological base whose implicit messages serve to make its viewers forget reality. Just as Levi Strauss believes that mythsplay a central role in society, Bibliowicz claims that the purpose of myths in telenovelas is to have us lose sight o f the origins of the eristingsocial order and to exonerate the dominant class which controls society's means of production. He gives us an overview of the Colombian television industry, describes how a telenovela is made, and analyzes one-“Manuela”-which contains a social message. Readers will find some interesting similarities and differences between this study of a Colombian popular art form and the articles by Flora and Bonilla de Ramos which focus on the fotonovela and radio in the same country.