Dosage and differential effectiveness of PREP, a home health nursing intervention for frail elders and family caregivers. This dissertation study built upon the research findings of the Family Care Study (PREP: Family-based Care for Frail Older Persons, ROI AG17909, 1999-2005) and focused on understanding the predictors of intervention dosage and whether variation in intervention dosage predicted the effectiveness of PREP, an in-home and telephone intervention for frail elders and their family caregivers. Specifically, it assessed whether the associations between three intervention dosage components (PREP nurse visits, PREP aide visits, and home health visits) and effectiveness is predicted by the care receiver (CR), caregiver (CG), or relationship variables.