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 German...

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