Computer Programs Mary C. Hill There are six postprocessors distributed with MODFLOWP, and integrated as subroutines into UCODE. Five of the six are documented in the report cited below. Three of these performed minor calculations that have since been integrated into MODFLOWP; while the separate programs are no longer distributed, the documentation still describes the resulting graphical analysis and their use. The other two of the five programs are still distributed with MODFLOWP and would be useful when combined with any nonlinear regression program. These are: YCINT, which calculates linear confidence and prediction intervals on predicted values, and BEALEP, which calculates Beale's measure, which indicates whether the model is linear so that the linear confidence intervals. The sixth postprocessing program, called RESANP and dedicated to residual analysis, is documented by Cooley and Naff (1990), was adapted to MODFLOWP (Hill, 1992), and was augmented for influential statistics by Richard M. Yager (WRR, in press). The three postprocessing programs YCINT, BEALEP, and RESANP are distributed with MODFLOWP and are present as subroutines in UCODE. It is hoped that these capabilities of these public domain programs will be used to enhance other nonlinear regression programs. Five Computer Programs for Testing Weighted Residuals and Calculating Linear Confidence and Prediction Intervals on Results from the Ground-Water Parameter-Estimation Computer Program MODFLOWP U.S. Geological Survey Open-File Report 93-481 Mary C. Hill ABSTRACT This report documents five computer programs, YR, NORM, BCINT, YCINT, and BEALEP, that use the results from the ground-water flow and parameter-estimation program MODFLOWP. MODFLOWP uses nonlinear regression to estimate parameter values. Programs YR and NORM produce data sets for two commonly used graphs of weighted residuals that are important in analyzing regression results. Programs BCINT and YCINT calculate linear confidence intervals on parameter estimates, and linear confidence and prediction intervals on simulated hydraulic heads and simulated flows along head-dependent boundaries [also, now, the three-dimensional components of advective travel]. These intervals are essential for displaying the reliability of simulated results, and can be used to make sensitivity analyses much more accurate than is allowed by traditional methods. Program BEALEP computes a measure of model linearity, which is needed to determine the accuarcy of the linear intervals calculated with programs BCINT and YCINT. This report includes a discussion of the purposes of all the programs and how results can be used, brief descriptions of the theory behind each program, illustrative examples of how the programs may be used, descritions of program input and output, and listings of the FORTRAN source codes. All of these postprocessing programs are distributed with MODFLOWP. The program and documentation can be downloaded from the USGS Ground Water software repository. mchill@usgs.gov Last Modified: March 21, 1999