Scientists performed an experiment to determine whether there is a connection between learning ability and food. They took two groups of 20 mice each, all from the same purebred strain. The mice were deprived of food for 3 days and then given a standard learning session in running through a maze. They were trained by giving them a mild electric shock whenever they took a wrong turn. Immediately after each learning session, one group of mice was fed, but the other was not, A week later, all of the mice were tested to see whether they could still run the maze correctly. The group that had been fed had retained this ability, but the other group had not. The probable reason that the scientists used only mice from the same pure-bred strain is so that?

This controls for one extraneous variable — other than the independent variable — that potentially can affect the dependent variable, so they must be controlled. If possible, you try to keep them constant between the experimental and control group.

The probable reason that the scientists used only mice from the same purebred strain is to minimize the genetic variation between the two groups of mice. By using mice from the same purebred strain, the scientists can rule out genetic factors that could potentially impact the learning ability and food connection being investigated in the experiment. Genetic variation can introduce additional variables and make it harder to draw clear conclusions about the specific relationship being studied. By controlling for genetic factors, the scientists can increase the internal validity of their experiment and have more confidence in the results.