Scientists investigated the spread of the rubella virus, which causes German measles. The first symptom is a distinctive red rash (spots) on the skin.
A group of 303030 children played together at a backyard party on Day 000. On the day of the party, one of the children developed a rubella rash.
Every two days after the party, scientists recorded how many of the other 292929 children first showed rubella spots. The results are shown in Table 1.
| Day when rubella spots first showed | Number of children |
|---|---|
| 6 | 0 |
| 8 | 0 |
| 10 | 0 |
| 12 | 2 |
| 14 | 3 |
| 16 | 8 |
| 18 | 5 |
| 20 | 1 |
| 22 | 0 |
| 24 | 0 |
| Total | 19 |
What was the range of days on which children first showed rubella spots? Use the data in Table 1.
From day ____________ to day ____________
Incubation time is the time from exposure to a pathogen until the first symptoms appear. Suggest the most likely incubation time for rubella based on this group.
Incubation time = ____________ days
Suggest one reason why some of the children at the party did not develop rubella.