Mark conducts a study for his research methods class to determine if consuming caffeine causes people to perform better on cognitive tasks. In his study, he gives half of his participants a glass of water and half of his participants a glass of cola and then has them attempt to solve 15 math problems. He finds that people who drink caffeine beforehand solve more math problems than those who drink water beforehand. Mark decides to conduct the exact same study again to ensure that he can find the same difference between the groups a second time. This study is known as a:

According to the federal regulations, which of the following studies meets the definition of research with human subjects? a researcher conducts a comparison of the comments made in a publicly available blog and the blogger's comments on a similar topic in a weekly magazine. undergraduate students in a field methods class are assigned a research question and asked to interview another classmate, to be followed by a class discussion on interview techniques. a cognitive psychologist enrolls undergraduate students for a computer-based study about the effect of mood on problem-solving behaviors. a researcher sets up a meeting with the superintendent of a large and diverse public school system to get data about the ethnic composition of the school system and the number of students receiving free lunches.