1. A computer-implemented method of determining the outcome of performing an aggregation-type operation on facts contained in a full structured collection of fact records, wherein the full structured collection of fact records is comprised of a plurality of component structured collections of fact records, the facts being data representative of interaction by users with information presented to the users via a computing network and each component structured collection of facts being for facts indicating user interaction during a particular time period the method comprising: by a computing system, sampling the plurality of component structured collections of fact records in a deterministic manner across the component structured collections of facts, wherein the sampling includes applying a sampling algorithm to values of a particular eminent attribute of the fact records consistently across the component structured collections of fact records, wherein the algorithm is characterized by deterministically distributing the fact records relative to the eminent attribute, the particular eminent attribute being a dimension of every one of the component structured collections of fact records, by the computing system, forming a merged collection of sampled fact records comprising the fact records sampled from the plurality of component structured collections of fact records, such that the merged collection of sampled fact records is longitudinal for records having the at least one particular eminent attribute value, over multiple time periods; by the computing system, performing an aggregation operation on the merged collection of sampled fact records to determine an aggregation result, the aggregation operates at a same level as the particular eminent attribute value and the aggregation result being an aggregate value representing an aggreate of the facts of the merged collection of sampled fact records; and by the computing system, based on the determined aggregation result and on an indication of characteristics of facts of the sampled fact records relative to the facts of the full structured collection of fact records, determining an indication of a statistical measure of a difference between what would be the result of the aggregation-type operation on the facts of the full structured collection of fact records and the actual result of the aggregation-type operation on facts of the sampled fact records, wherein the indication of the statistical measure of the difference indicates a confidence associated with the result of the aggregation-type operation on the sampled subset of facts.