GLM Syntax - Example 5: 2(k-p) Fractional Factorial
This example illustrates the specification for a fractional factorial 2(7-4) design. Use the example data file Cycling.sta. Note that a single two-way interaction (Tires*Breakfst) was added into the Design statement, even though only main effects can be estimated; the use of SSTYPE=5 will automatically delete all redundant higher order effects from the model (see Type V sums of squares for details). Further details concerning this data set and the analysis are also discussed in the context of the Experimental Design module (see Designing and Analyzing a 2**(7-4) Fractional Factorial Design).
GLM;
{ Dependent variable: }
DEPENDENT = TIME;
{ Specification of grouping variables (factors); note that
in this example, the numeric values (codes) are specified that
identify each group; these values are optional, and if left out,
the program would by default use all values (codes) found in the
data file. }
GROUPS = SEAT (1 -1)
DYNAMO (1 -1)
HANDLBRS(1 -1)
GEAR (1 -1)
RAINCOAT(1 -1)
BREAKFST(1 -1)
TIRES (1 -1);
{ A main-effects design is specified, with one additional interaction term. }
DESIGN = SEAT+DYNAMO+HANDLBRS+GEAR+
RAINCOAT+BREAKFST+TIRES+
TIRES*BREAKFST;
{ Type V sums of squares are requested: In the final model, for all effects
which are included in the model, all least squares means are estimable.
See Type V sums of squares for additional details. }
SSTYPE = 5;
For more examples, see GLM Syntax Examples.