What is a key characteristic of experimental research?

A key characteristic of experimental research is the use of random sampling and random assignment of research subjects. This approach allows for the establishment of causal relationships between variables by controlling for extraneous variables that could influence the outcome. Random sampling ensures that the subjects selected for the study are representative of the larger population, which enhances the generalizability of the results. Random assignment involves randomly placing subjects into different groups, typically an experimental group and a control group, thus minimizing biases and pre-existing differences between the groups before the intervention or treatment is applied.

This method is fundamental to experimental research because it enables researchers to draw more reliable conclusions about the effects of the independent variable being tested. On the other hand, the other options describe methodologies that are typical of non-experimental research or alternative research designs. For example, qualitative data methods focus on subjective data rather than quantitative measures; existing data refers to secondary data analysis rather than original data collection; and case studies offer deep insights into individual cases but do not provide the broad, controlled comparisons that characterize experimental methods.