A psychologist wants to know if the difficulty of a task influences our estimate of how long we spend working at it. She designs two sets of mazes that subjects can work through on a computer. One set has easy mazes and the other has hard mazes. Subjects work until told to stop (after six minutes, but subjects do not know this). They are then asked to estimate how long they worked. The psychologist has 30 students available to serve as subjects. (a) Describe the design of a completely randomized experiment to learn the effect of difficulty on estimated time. (Select all that apply.) Randomly decide (for each student) which set of mazes is used first. Compare the time estimates of Group 1 with those of Group 2. Each student does the activity twice, once with the easy mazes, the other time with the hard mazes. Compare the time estimates within each group for each type of maze. Randomly assign 15 students to Group 1 (easy mazes) and the other 15 to Group 2 (hard mazes). Compare each student's "easy" and "hard" time estimate.