A student used the internet to find information about caffeine and the possible effects it has on the body. The student decided to test the hypothesis that: Caffeine decreases the reaction time and increases the heart rate. Table 1.1 shows the results of the student's research into the caffeine content of drinks. Table 1.1 drink cup of coffee cup of tea 100 cm³ energy drink 350 cm³ cola caffeine content/mg 80 40 30 45 The student also found that it takes about 45 minutes before caffeine from a drink is fully absorbed into the blood and about 4 to 5 hours for the effect to wear off. After further research, the student decided: • test subjects should not know whether they are having a drink with caffeine or without caffeine • drinks with caffeine and without caffeine should look identical • to measure the subject's reaction time using a computer programme that flashes a coloured light at random intervals. The subject presses a switch as soon as they see the light • to measure the heart rate using a pulse meter attached to the first finger.