Abstract: A method for determining the probability that a biological molecule identification is incorrect for a chosen significance level is provided. The method includes comparing experimental mass data of an unknown biological molecule with theoretical mass data and calculating a score for each comparison; selecting at least two scores from the scores to form a primary data set; generating artificial data sets from the primary data set; calculating a sample mean for each artificial data set; estimating population mean and population standard deviation from the sample means wherein the population is based on the distribution underlying the primary dataset; computing a Z score from the population mean and population standard deviation for each score to standardize the scores; choosing a significance level; and comparing a test Z score to a Z score of the chosen significance level to determine the probability that the biological molecule identification is incorrect.