CHES (Certified Health Education Specialist) Practice Exam 2025 – Your All-in-One Guide to Exam Success!

An experimental trial is characterized by the random assignment of subjects to different conditions, which is fundamental to the design of experiments. This randomization helps to eliminate bias and ensures that any differences observed between the groups can be attributed to the manipulation of the independent variable rather than pre-existing differences among the subjects. By randomly assigning participants, researchers can more confidently infer causality and make generalizations about how changes in one variable may impact another.

The other aspects of the other choices do not accurately reflect the nature of experimental trials. Observational studies involve looking at subjects in their natural environments without manipulation, thereby not qualifying as experimental trials. Excluding control groups undermines the integrity of the experiment because control groups are essential for comparison and determining the effectiveness of the intervention. While long-term follow-up can be a feature of some experimental designs, it is not a defining characteristic of an experimental trial itself. Hence, random assignment is the critical element that distinguishes experimental trials from other research methodologies.