Based on prior knowledge, we can assume that the age group classification depends on the BMI ranges. In general, a body mass index (BMI) of 18.5 - 24.9 is considered normal weight, while a BMI of 25 - 29.9 is categorized as overweight. 

For this specific task, we can make the following assumptions:
- Adults typically have a wide range of BMI values, covering the normal weight, overweight, and obese categories.
- Seniors typically have a narrower range of BMI values, with more individuals falling into the overweight and obese categories.

Based on this analysis, we can create the following dictionary:

```json
{
    "Adult": [18.5, 22.5, 26.0, 30.3, 35.1],
    "Senior": [25.5, 27.8, 31.6, 36.9, 40.2]
}
```
Please note that these are just example values, and the actual values will depend on the dataset being analyzed.