A-LevelPsychologyResearch methods9990/21 · Oct/Nov 2020 · Q88 Marks

Elaf used a natural experiment to investigate the effect of noise on sleep. His participants completed identical questionnaires before the opening of a new motorway behind their houses and after the motorway had been open for one month.

(a)Explain what is meant by a 'natural experiment', using this study as an example.[2]
(b)Suggest one problem with natural experiments, using this study as an example.[2]
(c)(i)Identify the experimental design used in Elaf's experiment. Include a reason for your answer.[2]
(c)(ii)Explain one advantage of using this experimental design in Elaf's experiment.[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[1] (a) 1 mark for explanation
[1] (a) 1 mark for link
[1] (a) The IV cannot be manipulated = 1 (explanation)
[1] (a) Elaf could not control when the motorway opened = 1 (link)
[1] (a) The noise was due to the motorway or not = 1 (link)
[1] (a) So the two conditions of the experiment could not be controlled they had to be chosen = 1 (explanation)
[1] (b) 1 mark for problem
[1] (b) 1 mark for link
[1] (b) Participants (probably) cannot be allocated to different levels of the independent variable = 1 problem
[1] (b) There may be important individual differences, e.g. the worst sleepers went away on holiday when the motorway opened = 1 link
[1] (b) There are fewer controls than in a laboratory experiment = 1 problem
[1] (b) e.g. if people were more angry after the opening of the motorway and this made them sleep badly = 1 link
[1] (c)(i) 1 mark for identifying the experimental design Repeated measures DEFINITIVE
[1] (c)(i) 1 mark for reason
[] (c)(i) Answer must be linked for both marks
[1] (c)(i) Repeated measures is where the same participants are used in each level of the independent variable = 1 identify
[1] (c)(i) (All of) Elaf's participants do both the before/quiet/first test phase and the after/noisy/second test phase = 1 (linked) reason
[1] (c)(ii) 1 mark advantage
[1] (c)(ii) 1 mark link
[1] (c)(ii) (more valid as) Individual differences between participants aren't so important as each participant is his/her own baseline = 1 advantage
[1] (c)(ii) People sleep differently, e.g. badly or well generally, and this could distort the results if they were all in one group = 1 link
[1] (c)(ii) People are more or less sensitive to noise – 1 link