Marcus investigated the effectiveness of a new aggression replacement training (ART) programme for adult offenders on probation. He allocated the first 12 offenders who arrived at the probation office on Monday morning to the treatment group, and the first 12 offenders who arrived on Friday afternoon to the control group.
Explain one weakness of Marcus's investigation into the new aggression replacement training programme.
51 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.