A method for providing normalized physiological monitoring data of an individual with a measure of the quality of the normalization, including providing a reference feature based on a physiological attribute of the individual for which an attribute value can be determined; unobtrusively capturing physiological monitoring data for the individual during a series of capture events and determining the capture conditions present during each capture event; detecting the presence of the reference feature in the series of captured physiological monitoring data and determining associated attribute values for each capture event; normalizing the captured physiological monitoring data from each capture event according to differences in the attribute values associated with each event and previously calculated attribute values; and calculating normalization confidence values for the individual at the series of capture events, based on capture conditions, normalization transforms, or semantic data, wherein the confidence values statistically measure the quality of the normalization.