Psychology uses the scientific method to systematically study behavior and mental processes. The scientific method involves making observations, forming testable hypotheses, collecting data to test hypotheses, and reporting findings. There are four main goals of psychology: describe, explain, predict, and change behaviors. Researchers use a variety of methods including observational, correlational, and experimental studies. Experiments are powerful because they use random assignment to establish cause-and-effect relationships between variables. Strict research protocols are followed to ensure studies are valid, reliable, and ethical.