A biologist hypothesizes that keeping mice on a restricted diet with minimal calories will increase their aggression. The
biologist designs an experiment in which 100 mice are to be housed in individual cages under similar conditions and diets. He
then plans to place pairs of mice together in the same cage to observe their interactions. What is true about this study design?
A) The study is well designed since it uses a large sample of mice.
B) The study is not controlled.
C) The study includes too many variables.
D) The study is flawed because the hypothesis is not testable.
E) The study is unnecessary because the results are obvious.

The controlled experiment is an experiment where all the factors are held constant except the one factor that is meant to be tested. In the controlled experiment or study that includes a comparison of the experimental group with the control group in which all the factors or variables except the one factor being tested.

In these experiments there are not all the factors that are constant and also there is no control group to compare with the experimental group.

Thus, the correct answer is option B. the study is not controlled.