A study of the impact of caffeine consumption on reaction time was designed to correct for the impact of subjects’ prior sleep deprivation by dividing the 24 subjects into 12 pairs on the basis of the average hours of sleep they had had for the previous 5 nights That is, the two with the highest average sleep were a pair, then the two with the next highest average sleep, etc. One randomly selected member of each pair was allowed to drink two cups of caffeinated coffee, and the other drank two cups of decaf. Each subject’s performance on a standard reaction-time test was recorded. Which of the following is the correct check of the "Normal/Large Sample" condition for this significance tes