Question

a researcher follows the same group of participants from age 12 to age 20, but many participants stop responding over time. high dropout rates are especially problematic for which type of research? single - case research naturalistic observation cross - sectional research longitudinal research

Explanation:

Longitudinal research tracks the same group over an extended period. High dropout rates mean losing data from the original cohort, which undermines the core goal of observing changes in that specific group over time. The other methods do not rely on retaining the same participants across a long timeframe: single-case focuses on one subject, naturalistic observation is snapshot or short-term, and cross-sectional compares different groups at one time.

Answer:

Longitudinal research