Like many medical studies, the Berlin Aging Study II (BASE·II) is based on a non·random "convenience sample" of self·recruited participants. To study processes of selectivity in BASE·II, we used an identical questionnaire to compare BASE·II with a large, representative reference study, the...

Like many medical studies, the Berlin Aging Study II (BASE‐II) is based on a non‐random "convenience sample" of self‐recruited participants. To study processes of selectivity in BASE‐II, we used an identical questionnaire to compare BASE‐II with a large, representative reference study,...