SIZE
sizespecification ;
You use the SIZE statement to specify the size of the design, which is the number of runs in the design. The SIZE statement
is required for designs of less than a full replicate (for example, fractional factorial designs). By default, the design
consists of one full replication of all possible combinations of the factors.
The two simplest explicit sizespecifications that you can use are

DESIGN=n, which specifies the number of runs (n) in the design

FRACTION=h, which specifies of one full replicate
Use only one of these two options. In all, there are six mutually exclusive sizespecifications that you can use, as described by the following list:

DESIGN=n

specifies the actual number of runs in the design. The number of runs must be a power of the number of levels q for the factors in the design. (See the NLEV= option.) If the last FACTORS statement does not contain the NLEV= option, then q = 2 by default, and as a result, n must be a power of 2. For an example, see Example 7.1.

FRACTION=h

specifies the fraction of one full replication of all possible combinations of the factors. For instance, FRACTION=2 specifies
a halffraction, FRACTION=4 specifies a quarterfraction, and so on. In general, FRACTION=h specifies a design with of the runs in a full replicate. If the design has f factors, each with q levels, then the size of the design is . If you use FRACTION=h, h must be a power of q. See Example 7.4.

NRUNFACS=m

specifies the number of runindexing factors in the design. The design contains one run for each possible combination of the
levels of the runindexing factors. Runindexing factors are the first m factors for a design in runs. All possible combinations of the levels of the runindexing factors occur in the design. As a result, if each factor
has q levels, the number of runs in the design is . For details about runindexing factors, see Types of Factors and Structure of General Factorial Designs.

DESIGN=MINIMUM
FRACTION=MAXIMUM
NRUNFACS=MINIMUM

constructs a design with the minimum number of runs (no larger than one full replicate) given all of the other characteristics
of the design. In other words, the design size is optimized. You cannot specify this option if you specify any of the block
size optimization features in the BLOCKS statement (see NBLKFACS=MAXIMUM).
Equivalence of Specifications
The three explicit sizespecifications are related to each other, as demonstrated by the following example. Suppose you want to construct a design for 11 twolevel
factors in 128 runs. Since , three equivalent size specifications for this design are
size design=128;
size fraction=16;
size nrunfacs=7;
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