On defining at-risk status

You can include many in the at-risk group at the expense of including many not at-risk, or include few at the expense of missing many truly at-risk. The paper discusses the use of prevalence data and the relative costs of these two possibilities to help find the best way to separate at-risk and not-at-risk groups. The implications of the data being distributed normally are discussed, and several examples, including one with a nonnormal distribution, are given.