Final answer:
Random selection in research ensures an equal distribution of lurking variables across groups, allowing for valid cause-and-effect conclusions. Double-blind procedures further eliminate bias related to participant and researcher expectations, assuring accurate results.
Step-by-step explanation:
The random selection of research subjects into either the treatment or control group of a study is fundamental for maintaining the validity of the experiment's findings. By using random assignment, researchers ensure that potential lurking variables are distributed equally among the groups, which means that any observed differences in results should be attributed to the manipulation of the independent variable rather than preexisting differences. This is a crucial aspect of experimental design because it allows for the establishment of a cause-and-effect relationship between the explanatory (independent) variable and the response (dependent) variable being measured.
In double-blind studies, neither the researchers nor the participants know who belongs to which group, which controls for the placebo effect and expectations that could otherwise skew the results. Therefore, the random selection, combined with proper blinding procedures, helps to prevent bias and ensures that the study's conclusions are scientifically robust.