The current invention relates to a data mining technology for determining association rules within a multitude of N transactions each transaction comprising up to p different items. According to the invention a sample size n of the multitude of N transactions is determined based on precision requirements. The sample size n is chosen such, that it is at least in the order of magnitude of an estimated sample size n*. Finally association rules are computed based on a sample of the multitude of N transactions with sample size n according to any methodology for mining of association rules using the association rules as estimated association rules of the multitude of N transactions.