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Inference Models (inference + models)

Distribution by Scientific Domains

Life Sciences	33%

Selected Abstracts

Doubly Robust Estimation in Missing Data and Causal Inference Models

BIOMETRICS, Issue 4 2005
Heejung Bang
Summary The goal of this article is to construct doubly robust (DR) estimators in ignorable missing data and causal inference models. In a missing data model, an estimator is DR if it remains consistent when either (but not necessarily both) a model for the missingness mechanism or a model for the distribution of the complete data is correctly specified. Because with observational data one can never be sure that either a missingness model or a complete data model is correct, perhaps the best that can be hoped for is to find a DR estimator. DR estimators, in contrast to standard likelihood-based or (nonaugmented) inverse probability-weighted estimators, give the analyst two chances, instead of only one, to make a valid inference. In a causal inference model, an estimator is DR if it remains consistent when either a model for the treatment assignment mechanism or a model for the distribution of the counterfactual data is correctly specified. Because with observational data one can never be sure that a model for the treatment assignment mechanism or a model for the counterfactual data is correct, inference based on DR estimators should improve upon previous approaches. Indeed, we present the results of simulation studies which demonstrate that the finite sample performance of DR estimators is as impressive as theory would predict. The proposed method is applied to a cardiovascular clinical trial. [source]

Microanatomical diversity of the humerus and lifestyle in lissamphibians

ACTA ZOOLOGICA, Issue 2 2009
Aurore Canoville
Abstract A study of body size and the compactness profile parameters of the humerus of 37 species of lissamphibians demonstrates a relationship between lifestyle (aquatic, amphibious or terrestrial) and bone microstructure. Multiple linear regressions and variance partitioning with Phylogenetic eigenVector Regressions reveal an ecological and a phylogenetic signal in some body size and compactness profile parameters. Linear discriminant analyses segregate the various lifestyles (aquatic vs. amphibious or terrestrial) with a success rate of up to 89.2%. The models built from data on the humerus discriminate aquatic taxa relatively well from the other taxa. However, like previous models built from data on the radius of amniotes or on the femur of lissamphibians, the new models do not discriminate amphibious taxa from terrestrial taxa on the basis of body size or compactness profile data. To make our inference method accessible, spreadsheets (see supplementary material on the website), which allow anyone to infer a lissamphibian lifestyle solely from body size and bone compactness parameters, were produced. No such easy implementation of habitat inference models is found in earlier papers on this topic. [source]

Complexity versus integrity solution in adaptive fuzzy-neural inference models

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 5 2008
Georgi M. Dimirovski
This paper explores aspects of computational complexity versus rule reduction and of integrity preservation versus optimality index, which have become an issue of considerable concern in learning techniques for adaptive fuzzy inference models. In control-oriented applications of adaptive fuzzy inference systems, implemented as fuzzy-neural networks, a balanced observation of these conflicting requirements appeared rather important for a good yet feasible application design. The focus is confined to a family of adaptive fuzzy inference systems that can be interpreted as a partially connected multilayer feedforward neural networks employing Gaussian activation function. The knowledge base rules are designed implying the connections are a priori fixed, and then the respective strengths adapted on the grounds of input and output data sets. Information granulation plays a significant role too. These as well as membership-function parameters ought to be adapted in a learning-training process via the minimization of an appropriate error function. © 2008 Wiley Periodicals, Inc. [source]

Evolution of humeral microanatomy and lifestyle in amniotes, and some comments on palaeobiological inferences

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010
AURORE CANOVILLE
A study on the most exhaustive taxonomic sample of amniotes (75 extant and nine extinct taxa) of any quantitative work on this topic published so far demonstrates a strong relationship between lifestyle (aquatic, amphibious or terrestrial) and humeral microanatomy. We suggest that corrections for multiple testing be used to check for statistical artefacts in the context of a phylogenetic independent contrast analysis, and we use the false discovery rate procedure for this. Linear discriminant models segregate the various lifestyles with excellent success rate of up to 98.5%. Lifestyle was thus inferred for six extinct taxa of uncertain habitat. The results obtained suggest that Captorhinus, Claudiosaurus, and Placodus were amphibious, whereas Neusticosaurus and Mesosaurus were aquatic. Lystrosaurus may have been more aquatic than previously suggested, although the results of our inference models have to be integrated with other sources of data, which suggest that it may have been amphibious, rather than aquatic (as a literal interpretation of the models would suggest). Finally, we propose an alternative method of palaeobiological inference for hypothetical ancestors. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 384,406. [source]