1. A tuning data defect correction apparatus comprising:a defect analyzer to identify a suspect time window in tuning volume data of return path data reported by set top boxes; and
a return path data transformer to:
identify a first return path data entry indicating a first set top box reported a first transition to an off state at a first time during the suspect time window; and
modify the first return path data entry to (1) eliminate the first transition to the off state at the first time and (2) assign the first return path data entry a first duration to remain in an on state after the first time, the first duration determined based on monitoring data reported from media device meters monitoring media presentation devices.