Amara conducted an investigation to evaluate the effectiveness of a new anger management programme for young offenders. She allocated the first 15 offenders who volunteered to the treatment group, and another 15 offenders who were referred later to the control group.
Explain one weakness of Amara's investigation into the new anger management 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.