Abstract: A method of filtering data to predict an observation about an item for a particular case is provided in which: a set of data representing actual observations about a plurality of items for a plurality of different cases is modelled as a function of a plurality of case and item profiles, each profile being a set of parameters comprising at least one hidden metrical variable, the parameters defining characteristics of the respective case or item; a best fit of the function to the data is found in order to find the values of the item profiles; and the profiles found are used together with the function to predict an observation for a particular case about one or more items for which data is not available for that case.