Marcus conducted an investigation to evaluate the effectiveness of a new social skills training programme for violent offenders. He allocated the first 20 offenders who volunteered for the scheme to the treatment group, and another 20 offenders who were transferred to the facility later to the control group.
Explain one weakness of Marcus's investigation into the new social skills training programme.
Practise Edexcel A Level Psychology Research methods and skills with exam-style questions for A Level Psychology. 657 questions covering Research methods and skills, matched to the Edexcel A Level Psychology (9PS0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
