A public health researcher in a large city wants to understand sleep patterns among teenagers and young adults. She surveyed 80 residents aged 13–25 about the number of hours of sleep they get on a typical school/work night.
The results were compiled into the frequency table below. You will use this data throughout all four phases.
| Hours of sleep h | 4 ≤ h < 5 | 5 ≤ h < 6 | 6 ≤ h < 7 | 7 ≤ h < 8 | 8 ≤ h < 9 | 9 ≤ h < 10 | 10 ≤ h < 11 |
|---|---|---|---|---|---|---|---|
| Frequency | 3 | 7 | 18 | 24 | 16 | 9 | 3 |
The researcher stands at the entrance of a shopping mall on Saturday afternoon and asks every person who walks in until she has 80 responses. Name this sampling method. What is one potential source of bias?
Describe how she could instead use: (i) simple random sampling, (ii) systematic sampling, (iii) stratified sampling by age group (13–17 and 18–25). Which is most appropriate for this study? Justify your answer.
The city has 3 200 teenagers (aged 13–17) and 4 800 young adults (aged 18–25). How many from each group should appear in a stratified sample of 80? Show your full working.
You've worked through all four phases of the City Sleep Study.
Well done — get ready for the class consolidation.