Efficient learning in Approximate Bayesian Computation

Efficient learning in Approximate Bayesian Computatio

Variable selection for model-based clustering using the integrated complete-data likelihood

Variable selection in cluster analysis is important yet challenging. It can be achieved by regularization methods, which realize a trade-off between the clustering accuracy and the number of selected variables by using a lasso-type penalty. However, the calibration of the penalty term can suffer from criticisms. Model selection methods are an efficient alternative, yet they require a difficult optimization of an information criterion which involves combinatorial problems. First, most of these optimization algorithms are based on a suboptimal procedure (e.g. stepwise method). Second, the algorithms are often greedy because they need multiple calls of EM algorithms. Here we propose to use a new information criterion based on the integrated complete-data likelihood. It does not require any estimate and its maximization is simple and computationally efficient. The original contribution of our approach is to perform the model selection without requiring any parameter estimation. Then, parameter inference is needed only for the unique selected model. This approach is used for the variable selection of a Gaussian mixture model with conditional independence assumption. The numerical experiments on simulated and benchmark datasets show that the proposed method often outperforms two classical approaches for variable selection.Comment: submitted to Statistics and Computin

Bayesian model selection in logistic regression for the detection of adverse drug reactions

Motivation: Spontaneous adverse event reports have a high potential for detecting adverse drug reactions. However, due to their dimension, exploring such databases requires statistical methods. In this context, disproportionality measures are used. However, by projecting the data onto contingency tables, these methods become sensitive to the problem of co-prescriptions and masking effects. Recently, logistic regressions have been used with a Lasso type penalty to perform the detection of associations between drugs and adverse events. However, the choice of the penalty value is open to criticism while it strongly influences the results. Results: In this paper, we propose to use a logistic regression whose sparsity is viewed as a model selection challenge. Since the model space is huge, a Metropolis-Hastings algorithm carries out the model selection by maximizing the BIC criterion. Thus, we avoid the calibration of penalty or threshold. During our application on the French pharmacovigilance database, the proposed method is compared to well established approaches on a reference data set, and obtains better rates of positive and negative controls. However, many signals are not detected by the proposed method. So, we conclude that this method should be used in parallel to existing measures in pharmacovigilance.Comment: 7 pages, 3 figures, submitted to Biometrical Journa

The Role of Good Faith: A Case Study on the Application of Good Faith in the CISG

The work at hand discusses the role of ‘good faith’ in the meaning of Article 7 of the United Nations Convention on Contracts for International Sale of Goods (CISG). The CISG is a sales convention developed by UNCITRAL with the objective to provide a uniform and fair regime for the international sale of goods. As a consequence, the uniform application of the Convention is main concern of the CISG. Art. 7 provides a method to ensure that the Convention is applied in such uniform way. The provision lays down the three principles of interpretation of the CISG: ‘its international character’, ‘uniformity in its application’ and the ‘observance of good faith in international trade’

Student Preference On Exam Frequency: A Short Study

Examinations are used by most professors as an important assessment tool to aid in determining the level of student subject matter comprehension.  We also use the feedback from examinations as an indicator of the appropriateness and effectiveness of the teaching methodologies we are utilizing in the classroom.  This paper reports the number and types of exams/quizzes preferred by the students

The Role Of China And The United States In The Global Economy Of The 21st Century

The world is characterized by brutal global competition. When talking about competition during much of the 80s and 90s, we generally refer to the triage of Western European, Japanese, and U.S. firms. Today, we have to add firms from Brazil, Chile, China, and India to this elite bunch. This competition is good for the consumer -- prices of manufactured goods have been kept in check, and there is a general feeling of economic prosperity around the world. According to a recent article in The Economist global output has grown by over 4.3 % annually. The growing middle class in India and China has recorded the sharpest increase in the number of billionaires in the last decade; therefore the world has every reason to feel optimistically euphoric, even if China and India will reap a bigger share of the economic pie. In the words of Drucker, India and China are “…rapidly transforming their economies…they can now produce technologically sophisticated and financially rewarding offerings that are diminishing American standards.” (Drucker, 2004)  The concern with the advent of China has prompted more protectionist oriented legislation against China: textiles. The U.S. Congress also blocked a recent attempt by China’s China National Offshore Oil Corporation (CNOOC) to acquire Chevron. A recent Harris Poll indicated that 40% of the people surveyed believe that China will be stronger than the U.S. within a decade, and over 50% believe that China will have a negative effect on the U.S. economy

Student Preference On Exam Frequency: A Comparative Study Of St. Marys University And The American University Of Sharjah (UAE)

Most professors use examinations as an important assessment tool to aid in determining the level of student subject matter comprehension. We also use the feedback from examinations as an indicator of the appropriateness and effectiveness of the teaching methodologies we are utilizing in the classroom. This paper is a follow-up to a 2006-2007 study on the number and types of exams/quizzes preferred by the students with the addition of both ethnically and culturally diverse students from the American University of Sharjah