Open Minitab
From the data screen,name column 4 (C4) "Yield".
Enter the yields for the 9 runs in column 4, in the order obtained in overhead 3-33

Pull down menu: Statistics,DOE (Design of Experiments), Fractional Factorial. For "number of factors", enter 3.
For the "number of runs",enter 8. (This must be a power of 2] Click into the box under "Store data matrix (blocks and factors) in:", and type: c1-c3.

Click on the "Options" button; enter in the box ,"Number of Center Points" Click on the "OK" box. Click on the "OK" box again on the other screen.

Pull down the "Window" menu, "Data".
Low levels (25) are now represented with a (-1),
the high levels (75) with a (1), and the middle level (50) with a (0). (This is the conventional way to represent the levels; the fractional factorial screen allows the actual levels (25, 75, and 0) to be used instead)

Pull down the menu "Stats", "Regression", "Regression". Click on c4 "Yield", and click on the "Select" button.

Click on c1, hold down the button and move the mouse to Let go of the button, and click on the "Select" button.

highlight c1, c2, and c3