Elea is conducting an experiment to test whether people who sleep for more than eight hours per night are happier than people who sleep less than this.

Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

1. [1] By counting how many times the participant smiles (in an hour).
2. [1] Using a rating scale from 0–10 answering the question 'How happy do you feel?' (0 = not at all, 10 = very).
3. [1] With an interview asking them to describe their feelings and rating their response for happiness.
4. [2] There may be individual differences (e.g., in natural smile frequency, or how people interpret a 0-10 scale), which makes the measure subjective.
5. [2] Subjectivity could arise if interviewing or using open questions, as the researcher's interpretation of answers may differ from the participant's intended expression of happiness.
6. [1] Because people vary in terms of their need for sleep, so if 'long sleepers' were allocated to the 'short sleep' condition, they might feel ill/distressed or sleep deprivation could be dangerous.
7. [2] It reduces the effect of participant variables, so not all 'sleepy' participants end up in one condition (which would act as a confounding variable).
8. [2] It helps ensure that any observed differences in happiness are truly due to differences in sleep time, rather than pre-existing systematic differences between groups, allowing for stronger causal conclusions.
9. [3] **Opportunity sampling:** People are chosen because of their availability (e.g., from a nearby location) so they might not mind sleeping over in the lab.
10. [3] **Random sampling:** Every member of the population has an equal chance of being picked for the sample, so there would be a range of people with different normal sleep times.
11. [3] **Volunteer sampling:** People select themselves to be in the sample (e.g., respond to an advert for a study on sleep), so they would be likely to be willing to have their sleep changed/studied.