Dependability issues become more and more significant in RFID (Radio Frequency Identification) development and especially in critical domains. However, Operations of reading, detection of readers, and measurements of sensors in a RFID system are inevitably subjected to errors. These factors degrade the overall dependability of RFID systems. The authors study the Fault Tolerance in RFID systems as a means to ensure the dependability. The authors propose to perform a statistical analysis on the RFID tags data, using a confidence interval, at the level of the middleware enabling the detection of erroneous readers and sensors.