In a follow-up study, a health psychologist asked the same ten university students to take part in an experiment to compare two strategies designed to improve subjective sleep quality.
Condition 1: Five of the students were asked to follow a 'Sleep Sanctuary' protocol (removing all electronic screens from the bedroom) every night for a week.
Condition 2: The other five students were given blue-light filtering glasses to wear for two hours before sleeping every night for a week.
Each student's subjective sleep quality was measured at the start of the week and at the end of the week using a standardised self-report scale (where higher scores indicate better sleep quality quality).
| Sleep Sanctuary condition | Blue-light glasses condition | |||
|---|---|---|---|---|
| Start of week | End of week | Start of week | End of week | |
| Mean sleep quality score | 24 | 42 | 25 | 29 |
| Standard deviation | 6.2 | 2.1 | 5.8 | 5.5 |
What do the standard deviation values for the Sleep Sanctuary condition suggest? Justify your answer.
235 exam-style questions on AQA A Level Psychology Data handling and analysis. Each one has a worked solution and a mark scheme showing where the marks go.