The DataSwap software is a SAS® macro that was developed and maintained by Westat under contract with the National Center for Education Statistics/Institute of Education Sciences (IES)/Department of Education. The software conducts controlled random swapping. A user manual accompanies the SAS macro and provides the syntax for calling the macro, a technical description, and examples.
DataSwap employs a controlled random swapping approach by selecting records for swapping using different random sampling approaches (simple random sampling, stratified, probability proportionate to size). It selects swapping partners based on a distance (or bias) measure and can be used on data with complex samples. IES standard practice is to process the swapping five to seven times and review the global utility measures to recommend one of the runs.
For the controlled random swapping approach, "controlled" means two things: First, it means that the user is responsible for identifying the data swapping variables and parameters. The user/data analyst should be familiar with which data would be the most identifiable and sensitive. The user should also understand the content of the data file as well as the purpose and focus of the study so s/he can therefore guide the data swapping procedures accordingly.
The second meaning of "controlled" is that, in DataSwap, once the target records are selected, the file is partitioned into swapping cells. The swapping methodology is designed to find a swapping partner that limits data distortion. The methodology includes the use of swapping cells to identify swapping partners in adjacent cells with similar (or identical) weights and close (with at least one or some different) variable values. The pair with the smallest swapping bias is selected as the swapping partner.
Before implementing DataSwap, the user must consider several facets of the swapping process, including how the targets are to be selected, if particular records will be targeted for swapping, how the swapping cells are to be formed, and which variables will be swapped. Output reports help the user evaluate the swapping impact, which can also be controlled through the software parameters.