Sampling Wizard: Sampling Method

This step allows you to specify how to select cases from the active dataset.

Method. Controls in this group are used to choose a selection method. Some sampling types allow you to choose whether to sample with replacement (WR) or without replacement (WOR). See the type descriptions for more information. Note that some probability-proportional-to-size (PPS) types are available only when clusters have been defined and that all PPS types are available only in the first stage of a design. Moreover, WR methods are available only in the last stage of a design.

• Simple Random Sampling. Units are selected with equal probability. They can be selected with or without replacement.
• Simple Systematic. Units are selected at a fixed interval throughout the sampling frame (or strata, if they have been specified) and extracted without replacement. A randomly selected unit within the first interval is chosen as the starting point.
• Simple Sequential. Units are selected sequentially with equal probability and without replacement.
• PPS. This is a first-stage method that selects units at random with probability proportional to size. Any units can be selected with replacement; only clusters can be sampled without replacement.
• PPS Systematic. This is a first-stage method that systematically selects units with probability proportional to size. They are selected without replacement.
• PPS Sequential. This is a first-stage method that sequentially selects units with probability proportional to cluster size and without replacement.
• PPS Brewer. This is a first-stage method that selects two clusters from each stratum with probability proportional to cluster size and without replacement. A cluster variable must be specified to use this method.
• PPS Murthy. This is a first-stage method that selects two clusters from each stratum with probability proportional to cluster size and without replacement. A cluster variable must be specified to use this method.
• PPS Sampford. This is a first-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 specified to use this method.
• Use WR estimation for analysis. By default, an estimation method is specified in the plan file 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 defines the size of each unit. These sizes can be explicitly defined 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.