An apparatus and method for updating upper and lower thresholds in peak and valley systems. The apparatus includes comparators which determine which peaks or valleys are eligible for use in the calculation of upper or lower threshold levels. The comparators output the eligible peaks and valleys into statistical blocks that calculate the mean of the peaks and valleys as well as the deviation over a predetermined number of samples. Additional comparators compare either the mean deviation, standard deviation, or variance of the eligible peaks and valleys to predetermined deviation thresholds to determine whether the mean peak or mean valley should be used to calculate update thresholds. The apparatus further includes memory elements that store the mean peak or mean valley values used in the calculation of upper or lower thresholds.