5.
Process Improvement
5.3. Choosing an experimental design 5.3.3. How do you select an experimental design?


Full factorial designs in two levels  
A design in which every setting of every factor appears with every setting of every other factor is a full factorial design 
A common experimental design is one with all input factors set at two
levels each. These levels are called `high' and `low' or `+1' and `1',
respectively. A design with all possible high/low combinations of all the
input factors is called a full factorial design in two levels.
If there are k factors, each at 2 levels, a full factorial design
has 2^{k} runs.


Full factorial designs not recommended for 5 or more factors  As shown by the above table, when the number of factors is 5 or greater, a full factorial design requires a large number of runs and is not very efficient. As recommended in the Design Guideline Table, a fractional factorial design or a PlackettBurman design is a better choice for 5 or more factors. 