Cube Plots in Minitab

To create runs for a cube plot in Minitab, you select
Stat>DOE>Create Factorial Design.  On the main screen, you select
the Number of Factors (the default is 2--you'll want 3 for the 
homework) and then click on the Design button.  In the Design 
screen, select the design you want from the options listed (you'll 
want Full Factorial).  After entering your choices and returning 
to the main screen, click Options.  It's convenient to
have randomized runs when designing an experiment but inconvenient
when entering data for homework--click on Randomize Run Order to
remove this option.  

After returning to the main screen, you may want to click Factors 
in order to change the factor names (under the Name column) and 
levels (under the Low and High columns) to something that is more 
user-friendly.  For Problem 1 in HW 1, the factors are already 
labeled A, B, and C and would not need to be changed.  The factor
levels, though could be changed from -1 and 1 to S and M, respectively.
Click OK and your worksheet will have all the run levels entered and 
labeled.

You can enter your responses in an adjacent empty column (this will
be C8 for HW 1 Problem 1)--be sure to label the response column. For
the homework problem on variation, you will need to compute a measure
of spread (typically the standard deviation).  To do this, first
enter the replications from the 8 runs in 5 separate columns (C1-C5)
in a separate worksheet (create a new worksheet by selecting File>New
then selecting Worksheet). Note that the data is not in the order that
Minitab expects and you will need to rearrange the run order.  After 
entering the data, select Calc>Row Statistics, click on the 
Standard Deviation button, click in the Input Variables window, select 
C1-C5 as the input columns, then click in the Store Results In and enter
C6 by hand.  These standard deviations can then be cut and pasted into
your original worksheet as the response column.

To construct a cube plot, you select Stat>DOE>Factorial Plots. 
Check Cube and then click on Setup.  In the Setup window, 
double click on each of the three factors in the Available window, so
that they appear in the Selected window.  Click in the Response window
and then double click on your response column--it should appear in the
Response window.  Click OK in the Setup window and click OK in the
main window.  Your cube plot should appear as a separate graph window.