Factorial designs
involve testing several factors at two levels,
high and low. In a Full Factorial experiment
every possible combination of factors and
permutations is tested. If there are n factors
there are 2^{n} treatments.
The design matrix shows the combinations
for a 2^{2} design
Treatment 
A 
B 
AB

1 
1 
1 
+1 
2 
+1 
1 
1 
3 
1 
+1 
1 
4 
+1 
+1 
+1 
Refer to Fractional
Factorial Designs to see how a fractional
factorial design is created. 