As the size of the data is getting larger and larger due to improvement of the telecommunication techniques, it would be main issues to develop and process the database. The bloom filter used to lookup a particular element under the given set is very useful structure because of the space efficiency. In this paper, we introduce the error probabilities in Bloom filter. Especially, we derive the revised false positive rates of the Bloom filter using experimental method. Finally we analyze and compare the original false positive probability of the bloom filter used until now and the false decision probability proposed in this paper.