1. A quality control system in combination with an ECG data analysis system to analyze ECG data acquired by a hardware that includes an ambulatory electrocardiography device via a cable having a plurality of leads connected to a subject, comprising: a non-transitory medium having a plurality of programmable instructions for execution by a processor to perform the steps of: calculating a trend of a quality score in the ECG data acquired from the subject dependent on a noise content in the ECG data; and calculating a probability that one of a hardware and the Hookup personnel, each associated with collecting the ECG data from the subject, is a substantial cause of the quality score for the ECG data, wherein the probability is 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.