The programs RABBIT and MULTIPLY allow you to generate a number of daughter SNAP.DAT files from a parent SNAP.DAT file. The daughter files are identical to the parent file except that selected variables such as plasma , density, temperatures, neutral sources, etc., are varied from their nominal value in the parent file. By performing the usual SNAP analysis for each of the SNAP.DAT files, you can determine the uncertainty in derived quantities such as that results from uncertainties in the input diagnostic data and physics assumptions.