Which of the following is not true about dropout from longitudinal studies?

The statement that participants who drop out of a longitudinal study do not return is not true because it does not reflect the potential for re-engagement. In longitudinal research, participants may withdraw from the study for various reasons, but there are instances where researchers implement strategies to reconnect with those individuals. This could involve follow-up communications or interventions aimed at encouraging participants to rejoin the study.

The first option about participants dropping out at any stage is true, as longitudinal studies are characterized by their prolonged duration and ongoing data collection, allowing for dropouts to occur at multiple points. The ability for planned follow-ups to potentially re-engage dropout participants emphasizes the adaptability of longitudinal studies to maintain participant involvement. Lastly, the risk of biased results due to dropout is a recognized issue in research, highlighting the importance of addressing attrition through appropriate methodologies. Therefore, stating that once a participant drops out they cannot return underestimates the possibilities of participant engagement in longitudinal studies.