1. A cardiac monitor for detecting a cardiac event, the monitor comprising: (a) a sensor for sensing an analog signal from a human heart; (b) a device coupled to the sensor, the device having an analog-to-digital circuit system contained therein for digitizing the analog signal to produce a digitized waveform; (c) a processor electrically coupled to the analog-to-digital circuit system, said processor configured to: (i) compute a plurality of values of a heart signal parameter from the digitized waveform, the plurality of values of the heart signal parameter being characterized by a plurality of statistical distributions corresponding to a plurality of heart rates, wherein each statistical distribution is characterized by an upper boundary and a lower boundary and a dispersion; (ii) store data pertaining to the plurality of values of the heart signal parameter in a form that enables characteristics of first and second statistical distributions to be computed for first and second heart rates; (iii) determine a boundary value of the heart signal parameter associated with the second heart rate; (iv) determine a measure of the number of data points of the first statistical distribution, (v) operative when the number of data points indicates the first statistical distribution is insufficient, compute a detection threshold associated with the first heart rate, wherein the detection threshold is based on the boundary value of the heart signal parameter associated with the second heart rate. (vi) apply a test to detect a cardiac event, wherein the test is based on the detection threshold.