Alistair conducted a laboratory experiment to investigate the effect of lavender essential oil scent on spatial reasoning performance. He used an independent groups design where 12 participants completed a series of 15 mental rotation puzzles in a room diffused with lavender essential oil, and 12 participants completed the same puzzles in an unscented room. Each participant was given exactly 5 minutes. Alistair used opportunity sampling, recruiting the first 24 students who entered the university's student union bar on a Friday evening to participate.
Explain one improvement that Alistair could make to his investigation.
38 exam-style questions on Edexcel A Level Psychology Synoptic review of studies. Each one has a worked solution and a mark scheme showing where the marks go.