The following types of checks are carried out by the TwinLife team or the survey institute (detailed information about the procedures will be provided in a Technical Report):
1. Longitudinal consistency • variable pid, sex identical to prior waves • body height and weight • variable coding longitudinally consistent
2. Identity checks • match of sex, first name, date of birth, relationship to twins between preload and survey • checks for duplicates (persons included several times in the sample?) • change of surveyed sibling identified and corrected • household composition
3. Logical relations • age of twins vs. cohort • age vs. ptyp • age and sex of (biological) parents • twins’ age and sex identical • body height and weight
4. Completeness • Starting sample vs. realized sample (on personal, household, and family level) • Instrument/questionnaires vs. delivered variables
5. Instrument • Completeness and correctness of preload variables and generated filter variables • filter conditions
6. Variables • correctness of variable labels and value labels • correctness of missing values