Various committees within ASTM E08 are considering the possibility of making normalization a part of current standards or new standards in development. In these applications normalization would be used to determine crack lengths from the load displacement data obtained during a fracture test. Normalization assumes a continuous coupling between the three variables: load, load line displacement, and crack length. Given continuous information about any two of the variables and the boundary conditions on the third, the information between the boundary conditions can be resolved. An application for normalization would be to obtain a J-R curve from the continuous variables load and the load-line displacement with known boundary conditions of the initial and final physically measured crack lengths. The objective of this study was to determine the sensitivity of the output variables to the variability of the input parameters. Input parameters such as physically measured crack lengths, data spacing on the load COD graph, goodness of fit in the regression analysis, deviation allowance from the data to the fitted curve, and data cut off for normalized plastic displacement were varied in this study. The output variables to determine sensitivity were the JIC value and the J-R curve coefficients.