Eric designs a study to examine drink preferences of university freshmen. He is planning to have all of the freshmen who participate in his study drink a cup of coffee then rate their enjoyment of the coffee, then drink a cup of tea and rate their enjoyment of the tea, and finally drink a cup of milk and rate their enjoyment of the milk. Eric tells Theresa about the plans for his study and she says she is concerned that he could have a problem with order effect in his study. How can Eric fix this problem?

Counterbalancing.

Explanation:

In experiments, counterbalancing is the process that helps the researcher to control the effects of nuisance variables. Nuisance variables in the research are the variables that are unwanted and are of no value to the researchers.

Counterbalancing helps the researcher to make certain changes in the experiment by changing the ways of treatments to different participants in the group.

In the given case, Eric can fix the problem with order effect by counterbalancing, which will help Eric to eliminate unwanted variables from the experiment and change the ways of treatment to different participants.

So, the correct answer is Counterbalancing.