A quality control system in combination with an ECG data analysis system to analyze ECG data acquired by an ambulatory electrocardiography device via a cable having a plurality of leads connected to a subject is provided. The quality control system includes a memory having programmable instructions for execution by a processor to perform the steps of calculating a trend of a quality score in the ECG data dependent on a noise content in the ECG data and calculating a probability that one of a hardware and the Hookup personal, each associated with collecting the ECG data from the subject, is a substantial cause of the quality score for the ECG data. The probability can be calculated based on a comparison the trend of the quality score associated with the Hookup personnel versus the trend of the quality score of the hardware employed in acquiring the ECG data.
