To specify validation data for the currently selected fit, follow these steps:
Select Fit > Specify Validation Data. The Specify Validation Data dialog box opens.
Select variables for X data and Y data (and Z data for surfaces).
When you select two or three variables, depending on whether your fit data is for a curve or a surface, the tool calculates validation statistics (SSE and RMSE) and displays them in the Results pane and the Table of Fits. For definitions of these statistics, see Using the Statistics in the Table of Fits. Your validation data points display on the main plot and residual plot along with the original data.
Close the dialog box.