Final answer:
The method used to test relationships and examine cause-and-effect among variables is d) Experimental research, characterized by controlled conditions and variable manipulation. Participant observation is the technique likely used by a symbolic interactionist. Controlled experiments are necessary to establish causality in scientific research.
Step-by-step explanation:
The research method used to describe and test relationships and examine cause-and-effect interactions among variables is d) Experimental research. An experiment is a type of scientific investigation that is performed under controlled conditions. In an experiment, researchers manipulate an independent variable to see its effect on a dependent variable. By controlling for extraneous factors, researchers can establish causality between variables, making experiments a powerful tool in confirming the validity of a hypothesis.
For a symbolic interactionist, the research technique most likely to be used would be b) Participant observation. This qualitative research method involves the researcher immersing themselves in a social setting and making observations from an 'insider' perspective, which aligns with the interpretive frameworks common in symbolic interactionism.
Conducting experiments and using data are essential for establishing causal relationships in research. In the scientific context, a controlled experiment is essential for elucidating cause and effect, as opposed to observational studies or surveys which do not involve manipulation of an independent variable.