APA Dictionary of Psychology

in survival analysis, a research design that allows for the entry or exit of participants at any time throughout the course of the study. In a typical survival analysis design, all samples have a common origin—they start at the same time—and there is a single, terminal event (typically, death). By contrast, in a staggered entry design each participant begins the study at a particular time zero and has an ending point corresponding to the length of time that they were part of the study (i.e., until they experienced the event of interest or otherwise ceased participation). For example, consider a study of a new treatment method implemented at a specific hospital: There will be patients who survived over the entire study period, others who survived but entered the hospital after the study had already begun, and still others who moved away and lost contact with the researcher before the study was concluded.