A radio frequency identification (RFID) system for monitoring a space is disclosed. The system may include a controller connected with a plurality of RFID readers, where each reader can detect data signals from a plurality of RFID tags attached with objects. The objects may be part of an object category. The system may also have a database connected with the controller that records a time when the data signal is received from each tag in the plurality, and the data contained in the data signal from each tag in the plurality. The system may include a processor that can perform an inventory analysis of the objects based on a confidence probability curve. This curve may be a decaying function that may be based on various probabilities. Methods for using the confidence probability curve are also disclosed.