1. A method of controlling a nonvolatile memory device, comprising: receiving status register data for at least one memory cell, the status register data indicating a result of a read operation performed on the memory cell using a first read voltage; generating a command control signal based on status estimation information and a select signal, the status estimation information indicating an estimated status of the memory cell based on the status register data; re-reading the memory cell using a second read voltage having a value determined by the command control signal; and generating a coupling group index based on data reliability decision bits indicating reliability of data that has been re-read from the memory cell, additional data, and the select signal.