Centerpoint designs can be analyzed in Minitab by selecting Stat>DOE>Factorial>Create Factorial Design. Select the appropriate number of factors, then in the Designs... dialog box, select the design and specify the Number of Center Points. When you specify the factor levels, you do not have to specify the centerpoint levels; Minitab will do that automatically for you.
If you did not randomize the runs, the factorial points will appear first, followed by the center points.
Analyzing the data is straightforward, but it is important to link tests from our handouts to the Minitab output in the Session window. The centerpoint variance is the Mean Square Pure Error in the ANOVA table. The test for curvature appears in two places. It is the T test associated with the factor Ct Pt, and it also appears as the F test for Curvature. Note that the p-values are identical and the F statistic is the square of the T statistic.
The T statistics for the factor effects are computed as indicated in the handout; remember that the degrees of freedom is equal to n(c)-1; not the more familiar formula we have been using.
To create a contour plot, which can be useful when considering a steepest ascent direction, select Stat>DOE>Contour Plot, then select Contours... and choose Contour lines rather than Area. Click OK and you should have a contour plot. The Contour Plot tab is only available after an analysis has already been complete and does not work for two-factor designs.