The SIZE statement names one and only one size measure variable, which contains the sampling unit size measures that are used for selection with probability proportional to size. The SIZE variable must be numeric. When the value of an observation’s SIZE variable is missing or nonpositive, that observation is excluded from the sample selection.

The SIZE statement is required for all PPS selection methods, which include METHOD=PPS, METHOD=PPS_BREWER, METHOD=PPS_MURTHY, METHOD=PPS_SAMPFORD, METHOD=PPS_SEQ, METHOD=PPS_SYS, and METHOD=PPS_WR. For details about how size measures are used, see the descriptions of PPS methods in the section Sample Selection Methods.

Note that an observation’s size measure, specified in the SIZE statement and used for PPS selection, is not the same as the sample size. The sample size is the number of units to select for the sample, and you can specify the sample size with the SAMPSIZE= option.