Final answer:
Descriptive research is a method that describes behaviors and characteristics. Naturalistic observation observes behavior in its natural setting, while case studies focus on studying a few individuals in detail.
Step-by-step explanation:
Descriptive research is a research method that aims to describe and document behaviors and characteristics without manipulating or controlling them. It focuses on observing and recording data in its natural setting. Naturalistic observation is a type of descriptive research where behavior is observed in its natural context, such as observing children on a playground. Case studies are another type of descriptive research that involves studying a few individuals in detail over an extended period of time to gain a deep understanding of their behavior.