Final answer:
This situation is an example of deception in a research study.
Step-by-step explanation:
This situation is an example of deception. Deception is sometimes used in research studies to prevent participants' knowledge of the exact research question from affecting the results. In this case, Bill initially believed that someone on the research team was a fellow participant, but later learned the true identity of the team member and was fully informed about the purpose of the study. Deception is necessary in certain situations to maintain the integrity of the experiment, but participants must receive a full debriefing at the end of the study to provide complete, honest information about the experiment.