A researcher wanted to investigate whether a new blue-light filtering software application, "AuraShield", improves subjective sleep quality. Twelve participants who reported poor sleep quality participated in a 2-week study. The researcher compared the self-reported sleep quality scores (on a scale of 1 to 50) of participants during a baseline week with no app, to their scores during a second week using AuraShield.
Those participants whose sleep quality score increased during the week using AuraShield compared to the baseline week were categorised as 'improved' (+). Those whose sleep quality score decreased were categorised as 'worse' (-). Participants who had exactly the same score in both weeks were categorised as 'no change' (0).
Table 1: Participant sleep quality outcomes using AuraShield
| Participant | Improved (+) | Worse (-) | No Change (0) |
|---|---|---|---|
| 1 | - | ||
| 2 | + | ||
| 3 | + | ||
| 4 | 0 | ||
| 5 | + | ||
| 6 | - | ||
| 7 | + | ||
| 8 | 0 | ||
| 9 | + | ||
| 10 | + | ||
| 11 | - | ||
| 12 | + |
Explain two factors that the researcher had to take into account when deciding to use the sign test. Refer to the investigation described above in your answer.
121 exam-style questions on AQA A Level Psychology Inferential testing (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.