Alab researcher wants to find out whether mice will run through a maze quicker during the day or at night, after training. he has 100 mice available. he randomly assigns 50 of them into ech group. he trains the first group to run the maze ar 9: 00am and trains the sevond group to run the maze ar 9: 00 pm. each mouse is trained the same way, and the last 3 years run times are recored. describe what is being measured in this experiment and what variable is being manipulated?