Marcus conducted an experiment to investigate whether caffeinated energy drinks affect short-term memory recall. He asked a group of participants to consume a sugar-free energy drink containing 100mg of caffeine, wait 30 minutes, and then complete a digit-span recall task. One week later, the same participants were asked to consume an identical-tasting caffeine-free placebo drink, wait 30 minutes, and then complete an equivalent digit-span recall task.
Identify the independent variable (IV) in this experiment.
186 exam-style questions on Edexcel A Level Psychology Research methods and skills, covering Research methods and skills. Each one has a worked solution and a mark scheme showing where the marks go.