Practise explaining how randomised controlled trials are designed and evaluated in psychological research with CAIE Psychology AS questions and mark schemes.
From the key study by Grant et al. (2008) on treating gambling disorder with drugs and placebo:
Explain what is meant by a double-blind, placebo-controlled trial as used in this study.
Explain what is meant by a double-blind, placebo-controlled trial as used in this study.
Syllabus: 1.3.3 Key study on treating gambling disorder with drugs and placebo: Grant et al. (2008).
Marks: Double-blind: Award 2 marks for a detailed explanation. Award 1 mark for a partial explanation (definition).
Placebo controlled: Award 2 marks for a detailed explanation. Award 1 mark for a partial explanation (definition).
Answers may include (other appropriate responses to be credited):
- double-blind: an experimental procedure where neither the participant nor the researcher is aware of which condition the participant is in ( 1 mark) so a participant could be in the nalmefene (or naltrexone) group or the control (placebo) group and not know which group they are in (2 marks)
- placebo-controlled: a control group where no test medication is received but where the medication given has no actual effect, but the participant may think they are receiving the test medication (1 mark) so a participant could be in the nalmefene (or naltrexone) group or the control (placebo) group and not know which group they are in (2 marks).
Suggest one effect if a double-blind trial had not been used in this study.
Suggest one effect if a double-blind trial had not been used in this study.
Marks: Award 2 marks for an appropriate suggestion stated and applied to study with detail / elaboration / example.
Award 1 mark for an appropriate suggestion identified but not applied.
Answers may include (other appropriate responses to be credited).
Note: 'effect' could be on anything, not just validity.
Note: only one of the two possibilities below is required for 2 marks.
- participant bias: if a participant knows which group they are in, nalmefene (or naltrexone) group or the control (placebo) group, they might change their behaviour to support the aims of the study (or go against it) (2 marks).
- experimenter bias: if an experimenter knows which group a participant is in nalmefene (or naltrexone) group or the control (placebo) group, they may bias their behaviour toward the participant to support the aims of the study (2 marks).
Explain two strengths of conducting placebo-controlled trials in studies of gambling disorder.
Marks: up to 2 marks for each strength ×2
Award 2 marks for an appropriate strength stated and applied as required by the question with detail / elaboration / example.
Award 1 mark for an appropriate strength stated but not applied.
Answers may include (other appropriate responses to be credited):
Strengths:
- it is a control with a control group so there is a baseline to which the results of the experimental group can be compared (1 mark) and the effectiveness of the nalmefene (or naltrexone) on gambling disorder can be revealed (2 marks).
- it is a placebo and so the participant will behave as if they are in the experimental group (1 mark) because they do not know whether they are in the nalmefene (or naltrexone) group or the control (placebo) group (2 marks)