The graph below shows the results of an experiment in which mice learned to run through a maze. List some variables that must have been controlled so as not to affect the results.

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1. Identify the independent variable in the experiment, which is the type of reward given to the mice (no reward vs. food reward). This variable is manipulated to observe its effect on the dependent variable.
2. Recognize the dependent variable, which is the average time it takes for the mice to complete the maze (measured in minutes). This is the outcome being measured in response to the independent variable.
3. List potential controlled variables that must remain constant to ensure the validity of the experiment. Examples include: the maze design (same layout for all mice), the age and species of the mice (to ensure similar physical and cognitive abilities), and the time of day the experiment is conducted (to avoid variations in activity levels).
4. Consider environmental factors that must be controlled, such as lighting, noise levels, and temperature in the testing area, as these could influence the mice's behavior and performance.
5. Ensure that the number of trials and the duration of the experiment are consistent for all groups of mice. For example, all mice should have the same number of days to practice running through the maze and the same number of attempts per day.