Some students do homework with the TV on. Researchers wanted to see if people can work as effectively with distractions as without them. From a group of student​ volunteers, researchers randomly assigned half to do a relatively easy crossword puzzle in a quiet room and the other half to do the same crossword puzzle in a room in which a TV was on. Then each volunteer was to do a different relatively easy crossword puzzle under the other condition. Students were timed on how long it took to complete the puzzle and the difference in each​ student's quiet-room time and​ TV-room time was recorded. Which test is appropriate to use to determine if students take longer to complete the puzzle in the TV room compared to the quiet​ room, on​ average?