Based on prior knowledge, we can assume that Body Mass Index (BMI) ranges are commonly used to categorize weight status in individuals. In this case, we can analyze how the BMXBMI feature relates to the target variable "Age Group" (Senior or non-senior) to determine the appropriate ranges of values.

To create the dictionary, we need to identify typical BMXBMI values for each target class. Let's assume the following age ranges:
- Adult: 18-64 years
- Senior: 65+ years

Here is an analysis of the relationship between the BMXBMI feature and the target variable:

- Adult:
  - Typical BMXBMI values for the Adult class may include:
    - 20.5
    - 22.3
    - 25.1
    - 27.8
    - 30.2

- Senior:
  - Typical BMXBMI values for the Senior class may include:
    - 21.8
    - 23.7
    - 26.3
    - 29.9
    - 31.5

Based on this analysis, we can create the dictionary:

```json
{
    "Adult": [20.5, 22.3, 25.1, 27.8, 30.2],
    "Senior": [21.8, 23.7, 26.3, 29.9, 31.5]
}
```