Full Factorial Designs¶
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.
TABLE 3.2 Number of Runs for a \(2^k\) Full Factorial
| Number of Factors | Number of Runs |
|---|---|
| 2 | 4 |
| 3 | 8 |
| 4 | 16 |
| 5 | 32 |
| 6 | 64 |
| 7 | 128 |
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. A fractional factorial design or a Plackett-Burman design is a better choice for 5 or more factors.