Abstract
Bayesian implicative analysis was proposed for summarizing the association in a $2\times 2$ contingency table in terms possibly, asymmetrical such as, \eg, ``presence of feature $a$ implies, in general, presence of feature $b$'' (``$a$ quasi-implies $b$'' in short). Here, we consider the multivariate version of this problem: having $n$ units which are classified according to $\Qcard$ binary questions, we want to summarize the association between questions in terms of quasi-implications between features. We will first show how at a descriptive level the notion of implication can be weakened into that of quasi-implication. The inductive step assumes that the $n$ units are a sample from a $2^\Qcard$-multinomial population. Uncertainty about the patterns' true frequencies is expressed by an imprecise Dirichlet model which yields upper and lower posterior probabilities for any quasi-implicative statement. This model is shown to have several advantages over the Bayesian models based on a single Dirichlet prior, especially whenever $2^\Qcard$ is large and many patterns are thus unobserved by design.
Keywords. Quasi-implication, logical model, measure of association, multivariate implicative index, Boolean methods, Bayesian inference, upper and lower probabilities.
The paper is available in the following formats:
Authors addresses:Laboratoire Cognition et Activités Finalisées
E-mail addresses:
| Jean-Marc Bernard | berj@univ-paris8.fr |