A physiological monitoring system may determine physiological information, such as physiological rate information, from a physiological signal. The system may select two segments of the physiological signal, shifted in time relative to one another by a lag value, and determine a correlation value between the two segments. The system may determine a metric based on the segments, and determine correlation information based on the correlation value and the metric. The metric may be indicative of how well the segments are correlated, providing additional information relative to the correlation value. Based on the metric, the system may modify the correlation value, determine a confidence value, or determine other information. The system may determine physiological rate information based on the correlation information.