Final answer:
Relationship experiments are designed to investigate and test the relationship between two variables. Their primary purpose is to gather evidence and test hypotheses.
Step-by-step explanation:
Relationship experiments are designed to investigate and test the relationship between two variables. These experiments allow researchers to manipulate the explanatory variable and observe the response variable to examine cause-and-effect relationships. Their primary purpose is to gather evidence and test hypotheses in order to better understand and explain social phenomena.