IBM SPSS COMPLEX SAMPLES 19 Water System User Manual


 
9
Sampling from a Complex Design
PPS Systematic. This is a rst-stage method that systematically selects units with probability
proportional to size. They are selected without replacement.
PPS Sequential. This is a rst-stage method that sequentially selects units with probability
proportional to cluster size and without replacement.
PPS Brewer. This is a rst-stage method that selects two clusters from each stratum with
probability proportional to cluster size and without replacement. A cluster variable must be
specied to use this method.
PPS Murthy. This is a rst-stage method that selects two clusters from each stratum with
probability proportional to cluster size and without replacement. A cluster variable must be
specied to use this method.
PPS Sampford. This is a rst-stage method that selects more than two clusters from each
stratum with probability proportional to cluster size and without replacement. It is an
extension of Brewer’s method. A cluster variable must be specied to use this method.
Use WR estimation for analysis. By default, an estimation method is specied in the plan le
that is consistent with the selected sampling method. This allows you to use with-replacement
estimation even if the sampling method implies WOR estimation. This option is available
only in stage 1.
Measure of Size (MOS). If a PPS method is selected, you must specify a measure of size that denes
the size of each unit. These sizes can be explicitly dened in a variable or they can be computed
from the data. Optionally, you can set lower and upper bounds on the MOS, overriding any values
found in the MOS variable or computed from the data. These options are available only in stage 1.