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:
See the answers below in Related Questions.
The different strain might be a confounding variable.
http://www.google.com/search?client=safari&rls=en&q=Medical+terminology&ie=UTF-8&oe=UTF-8
The probable reason that the scientists used only mice from the same purebred strain is to control for genetic variability. By using mice from the same purebred strain, the scientists ensured that any differences in learning ability observed between the fed and non-fed groups could be attributed to the food deprivation and not to genetic variation between the mice.
Using mice from the same purebred strain helps to minimize the effects of genetic factors on learning ability. This is important because if the mice used in the experiment came from different genetic backgrounds, their ability to learn and retain information in the maze could be influenced by their genetic differences rather than the experimental manipulation (food deprivation). By using mice from the same purebred strain, the scientists can be more confident that any observed differences in learning ability are due to the manipulation of food deprivation.
Controlling for genetic variability is a fundamental practice in experimental design to ensure that the results are more reliable and generalizable. It allows researchers to isolate the effects of the manipulated variable (in this case, food deprivation) and draw more accurate conclusions about the relationship between learning ability and food.