This document discusses research principles and methods for studying child and adolescent development. It introduces the scientific method as an important research principle, outlining the typical steps of identifying a problem, determining a hypothesis, collecting and analyzing data, formulating a conclusion, and applying conclusions to the original hypothesis. Several research designs used in developmental research are described, including case studies, correlational studies, experiments, naturalistic observation, longitudinal studies, cross-sectional studies, sequential studies, and action research. Ethical principles that guide researchers to protect participants are also covered.