One of the goals of the evaluation was to produce data for public use after the initial evaluation was completed. Thus, in developing the project data files and documentation, we always had the outside uses in mind. The principles followed in selecting data for public use were as follows:
All data that were used in the analyses should be available so that evaluation analyses could be replicated from the files.
Principle (1) should be achieved subject to maintaining the confidentiality of data.
As much data as possible should be included in the public use files.
Although the preparation of the public use files was always planned, their implementation occurred over the last six months of the project, to ensure that all variables used in analyses were available and documented for inclusion in the files.
The public use files were prepared from the project's data base. This data base was designed in the first 18 months of the project, and implemented in March 1982 at the time that screening and sample member randomization began. As new instruments were designed, pretested, and cleared by OMB, the data base was expanded to include new files.
Sample intake occurred over a period of 15 months, and primary data collection continued until July 1984, providing up to 18 months of followup. Secondary data associated with the followup period (claims data, death records, and provider records) continued to be acquired over the ensuing four months.