Rodney is involved in a study to examine the long-term effects of caffeine on excitability. there are two groups in the study—one group will be given caffeine tablets twice a day, and one will be given a placebo twice a day. in this study, neither the researchers nor the participants know who will receive caffeine and who will receive the placebo. based on this information, you are able to determine that rodney is participating in what type of study:

This is an example of a double-blind type study.

Explanation:

Neither the researchers nor the participants know whether they are receiving caffeine or not. Thus there are no behaviors that people might observe due to bias. If the researcher was convinced that the caffeine tablets would increase excitability, and knew who was taking actual caffeine, then this bias could result in incorrect assessments of behavior.

If the subjects knew that they were taking placebos for example, then they might suppress all evidence of excitability, even in the face of events that might be expected to cause a normal excited response.

Therefore, the double-blind type of study is expected to produce the least biased behaviors and observations.