The development of the error prone model (EPM) for the 1984-1985 student financial aid validation criteria for Pell Grant recipient selection is discussed, based on a comparison of the 1983-1984 EPM criteria and a newly estimated EPM. Procedures/assumptions on which the new EPM was based include: a sample of 1982-1983 Pell Grant recipients originally selected for the Pell Grant Quality Control Study was used for estimation; cases assumed to have met the Pre-Established Criteria were excluded from the estimation database; and the model was based on an exploratory data analysis approach embedded in the Automatic Interaction Detector (AID) software package. To develop the new EPM, error was defined as the potential change in the Student Aid Index resulting from validation on four application items: household size, U.S. taxes, and adjusted gross income of dependent parents or independent students, and student/spouse net income for dependent students. The 41 applications items that were considered as possible variables for predicting errors are identified. Information is also provided on the 18 final groups that emerged from the AID sequential search estimating procedure. Appended are descriptions of the 28 validation criteria for 1984-1985. (SW)