Factor Names
Optionally, specify names for the factors. In the example, you are creating a design with two variables, each of which have two possible levels. The syntax for this field is
c("variable one factor name one", "variable one factor name two"), c("variable two factor name one", "variable two factor name two"))
Use the Zoom feature to make editing this field easier. Right-click on the field, and choose Zoom. In the Zoom edit box, type the factor names as described, and click OK.
If factor names are not given, they default to A, B, etc. If levels are not given, they default to the factor name (possibly abbreviated) followed by level numbers.