Dr Vance is researching whether listening to binaural beats improves focus in high school students during self-study. He posts a call for participants on the school's online student portal, asking interested students to click a link to sign up.
Identify the sampling technique used by Dr Vance in this study.
638 exam-style questions on Edexcel A Level Psychology Methods. Each one has a worked solution and a mark scheme showing where the marks go.