Experimental designs are structured approaches used in research to test hypotheses and determine cause-and-effect relationships. They involve manipulating one or more independent variables while controlling for other factors, allowing researchers to observe the effects on a dependent variable. Common types of experimental designs include randomized controlled trials, factorial designs, and cross-over designs. These designs help ensure that results are valid and reliable by minimizing biases and confounding variables. By using techniques like random assignment and blinding, researchers can enhance the credibility of their findings, making experimental designs a cornerstone of scientific inquiry in fields such as psychology, medicine, and social sciences.