Enhancements on the decision threshold algorithm of the net count calculation method

For the net count calculation method, decision thresholds of net numbers of counts are underestimated if the gross numbers of counts are below numbers of detector background counts. A priori knowledge of non-negative radioactivity was used to estimate interferences and the memory effect. The baselines of decision thresholds are estimated by the spectrum of a hypothetical sample in which net numbers of counts were all equal to zero. No decision thresholds for low count samples are below the baselines.