To set the holding level for variables not in the plot for a factorial design
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1    In the Overlaid Contour Plot dialog box, click Settings.

2    Do one of the following to set the holding value for extra variables or covariates:

·    To use the preset values for variables, covariates, or process variables, choose High settings, Middle settings, or Low settings. When you use a preset value, all variables not in the plot will be held at their high, middle (calculated median), or low settings.

·    To specify the value at which to hold the variable, covariate, or process variable, enter a number in Setting for each of the design variables you want control. This option allows you to set a different holding value for each variable.

3    Click OK.