In factoral design, a factor is a major independent variable. A level is a subdivision of a factor. Take an example as $3 \times 3$ factoral design. Suppose an investigator wants to examine three components of a weight loss invervention as,
- Keep a food diary(yes/no)
- Increasing activity(yes/no)
- Home visit(yes/no)
There are three factors and each factor has two levels, that is a $2^3$ factoral design. 8 different conditions exist.
Fractional Factorial design
