An educational psychologist is investigating whether classroom temperature affects reading comprehension. Group A completed a reading task in a classroom kept at a warm 26∘C26^\circ\text{C}26∘C, while Group B completed the same task in a classroom kept at a cool 19∘C19^\circ\text{C}19∘C. All participants, regardless of group, were given exactly 12 minutes to complete the reading comprehension task, which was printed in identical booklets. However, participants were tested at various times between 9:00 AM and 4:00 PM depending on their availability, and they were allocated to groups based on their arrival time.
| Participant: Group A (Warm) | Comprehension score (out of 30) | Participant: Group B (Cool) | Comprehension score (out of 30) |
|---|---|---|---|
| 1 | 18 | 1 | 24 |
| 2 | 22 | 2 | 27 |
| 3 | 15 | 3 | 21 |
| 4 | 19 | 4 | 25 |
| 5 | 21 | 5 | 23 |
| 6 | 17 | 6 | 26 |
| 7 | 20 | 7 | 22 |
Which extraneous variable has been controlled for in this research?
Time of day of testing
Duration of the task
Baseline reading ability of participants
Participant allocation bias
