Data management
Data from questionnaires are entered by trained research assistants. We use forms created with Microsoft Access for data entry. When entering the data, the research assistants can only select from a set of valid values. The first 20 questionnaires of each of the four measurement points and subsequently every 20th questionnaire are re-entered by a second independent person. Incorrect completion of questionnaires (e.g., multiple crosses) are logged. Data entries are made immediately when the questionnaires are available to the University of Lübeck. The presence of the questionnaires at the beginning and end of the rehabilitation is documented in the study list of the rehabilitation center. The same applies to the mailing of the 3-month and 12-month follow-up questionnaires. The questionnaires received after 3 and 12 months are documented at the University of Lübeck. The identification numbers of the incoming questionnaires are transmitted by the University of Lübeck to the rehabilitation center. If receipt is confirmed by the University of Lübeck, no reminder is sent. A comprehensive plausibility check is performed for all data prior to our analysis of the data.