When you have a student take a quiz, tell them to make their best guess, if they don't know the answer. They should not just go through checking every box. Make sure that they know that this is a purely educational quiz. They will not be punished for poor performance, we simply want to be sure that they know what they are doing. After the student is finished with the quiz, click on the button that says "supervisors click here". This will display the input log, it tells you the total number of times they clicked a box that was wrong, and one that was right. The display should read "Wrong answers 8/12", this means that they checked 8 out of the 12 answers that were incorrect. Similar information is provided for right answers. If the display reads 12/12, 11/12, or even 13/12 wrong answers, it means that they probably just checked each and every box.
It also lists each answer the student selected, in the order they were selected. You should look at the answers that they got wrong and make sure the student knows why they were wrong. Also check and make sure they checked all the right answers.
When you are done, and another student is ready to take the quiz make sure you first hit the, "clear this quiz" button at the bottom, and then hit the "reload" button in the navigation bar. If you only hit the "clear this quiz" button, then the quiz will be cleared, but the input log will not.
Try taking the quiz yourself to see how the input log works.