Define extraneous variables and uncontrolled variables, using any examples.

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

1. Award 1 mark for each definition, up to a maximum of 2, for each type of variable.
2. Award 1 mark for each example that is linked to one type of variable, up to a maximum of 2, for each type of variable.
3. Examples can include examples from any studies or including imagined ones.
4. extraneous variables
5. are any variables that can affect the DV (other than the IV);
6. and this effect can be random;
7. e.g. if some participants in a study were hungry and worked faster to get home;
8. which is less of a problem;
9. or it can be systematic;
10. and affect one level of the IV more than the other, resulting in a biased result/ error;
11. e.g. if one condition was before lunch and all the participants were hungry so worked harder (and the other condition was after lunch so they were not hungry and worked more slowly);
12. e.g. in Bandura's study the children's aggression was an extraneous variable (that was controlled);
13. these are called confounding variables / ie they confound the results;
14. these variables can be controlled (if they are identified);
15. uncontrolled variables
16. are variables that have not been identified as a problem;
17. or have not been /cannot be successfully eliminated;
18. so limit validity;
19. because they can affect one level of the IV (more than the other);
20. e.g. the weather;
21. demand characteristics can cause uncontrolled variables;
22. e.g. if it is obvious to one people in one level of the IV but not the other that they are in an experiment;