Elena conducted a correlational study to investigate whether there was a relationship between daily caffeine intake (measured in milligrams) and the duration of rapid eye movement (REM) sleep (measured in minutes).
Outline one strength and one limitation of using a correlational research design in this investigation.
82 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.