Researchers examined whether short-term sleep deprivation affects complex problem-solving. volunteers refrained from caffeine for hours. At , they were randomly assigned to two conditions. Condition A slept for a full hours in the lab, and Condition B was kept awake all night. At , all subjects completed a timed reasoning battery and reported their subjective sleepiness. The researchers also measured baseline IQ and recent caffeine consumption. Which factors might impact the response variable are cited in the description? Which factor is manipulated? How many levels are there for the manipulated factor?
