The Society for Imprecise Probabilities: Theories and Applications (SIPTA) is a not-for-profit organisation that aims to promote research on imprecise probabilities. It does so by organising events that bring together researchers, by creating resources for information, dissemination and documentation, and by making other people aware of the potential of imprecise probabilities. SIPTA is run by its executive committee, according to the directives outlined in its articles and bylaws. Changes to these articles and bylaws are voted upon at the SIPTA general meetings.
The term imprecise probabilities is understood in a very wide sense. It is used as a generic term to cover all mathematical models which measure chance or uncertainty without sharp numerical probabilities. This includes both qualitative models (such as comparative probabilities, partial preference orderings and choice functions) and quantitative ones (such as sets of probabilities, interval probabilities, belief functions and upper and lower previsions). Imprecise probability models are needed in inference problems where the relevant information is scarce, vague or conflicting, and in decision problems where preferences may be incomplete.
SIPTA was created in February 2002. It has its roots in the Imprecise Probabilities Project, conceived in 1996 by Peter Walley and Gert de Cooman, and its creation has been encouraged by the success of the ISIPTA conferences. Some documents from the early days of SIPTA are still available in the SIPTA archive.