Participants in their study first completed two tasks, a placekeeping task [UNRAVEL] and a Psychomotor Vigilance Task [PVT] and then were randomly assigned to either stay up all night in the lab, or go home to sleep. The next morning, the sleep group returned to the lab and all participants were randomly assigned to consume either a placebo or 200 mg of caffeine in capsule form. Participants then completed the two tasks again. Findings showed that sleep deprivation impaired performance on both tasks, but caffeine improved performance in the PVT but not the UNRAVEL task. Based only on information provided above and the graphic figure below... Figure 2 Estimated Morning Event Rates for the Psychomotor Vigilance Task (PVT) and the UNRAVEL Task 25 .25 PVT lapses .20 20 Placebo Caffeine Estimated morning event rates .15 10 .10 .05 UNRAVEL post- interruption errors UNRAVEL non- interruption errors .00 Sleep Sleep- deprived Sleep Sleep- deprived Sleep Sleep- deprived a. Identify the two independent variables (IV), providing either the name of the concept being examined and/or the research definition of that concept. b. State specifically how each IV is operationalized. C. Indicate whether each IV is a manipulated or measured variable.