What type of study design was used in Milgram's research?

The study design used in Milgram's research is classified as a lab experiment. This means that the experiment was conducted in a controlled environment where the researcher could manipulate variables and maintain strict control over extraneous variables. In Milgram's study, participants were placed in a setting that simulated a learning environment, and they were assigned the role of "teacher," while the confederate acted as the "learner."

The key features of a lab experiment, such as the controlled conditions and structured procedure, allowed Milgram to observe the effects of authority on obedience in a systematic manner. By having participants believe they were administering electric shocks to another individual, Milgram could effectively measure the impact of situational variables on behavior, contributing to our understanding of obedience to authority figures.

In contrast, the other options represent different methodologies that have distinct characteristics. A field experiment takes place in a natural setting rather than a controlled lab environment, a correlational study examines relationships between variables without manipulation, and a case study focuses on an in-depth exploration of a single individual or group. Each of these alternatives lacks the rigorous control and manipulation characteristic of lab experiments, which is why Milgram's study is specifically categorized under this design.