Olivia is conducting an experiment to investigate whether students concentrate better in class before or after eating. Her experimental design is a repeated measures design.

Mark scheme

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

1. [1] (a) When the students eat (before or after class).
2. [1] (b) Concentration in class.
3. [1] (c) A repeated measures design means the same group of participants takes part in all levels or conditions of the independent variable (explanation).
4. [1] (c) In this experiment, all participants are tested both before eating and after eating (link).
5. [1] (d)(i) By having different groups of participants complete the conditions in different orders (generic suggestion).
6. [1] (d)(i) For example, one group of students could be tested before eating on one day and after eating on the next, while another group is tested after eating on the first day and before eating on the second day (link).
7. [1] (d)(ii) Counterbalancing controls for order effects, such as fatigue or practice effects (generic advantage).
8. [1] (d)(ii) This prevents factors like participants being bored or tired during the second test, or getting better due to practice, from affecting the results of concentration (link).