A researcher is interested in the effects of a vegetarian diet on memory. One group eats a strict vegetarian diet for three months, a second group eats a strict vegan diet for three months, while a third group eats anything they want for three months. After three months, all participants are given a memory test. The first 20 people who participated were assigned to the vegetarian group, the next 20 to the vegan group, and the final 20 to the eat anything group. What's wrong with this experiment?
A)It is confounded because of a possible experimenter bias effect.
B)The experimenter introduced some demand characteristics.
C)It is confounded because there was no random assignment.
D)It is confounded because the study cannot be replicated.
E)There is nothing wrong with this experiment.

Question

Quizplus · Accepted Answer

The lack of random assignment to the different diet groups means that any observed differences in memory test performance could be due to pre-existing differences between the groups rather than the effect of the diet itself.

A Researcher Is Interested in the Effects of a Vegetarian