To analyze the relationship between the feature "BMXBMI" and the target variable (age group), we can assume that higher BMI values may indicate a higher likelihood of being a senior. However, it's important to note that BMI alone may not be the most accurate indicator of age. Additionally, the specific ranges of BMI values for different age groups may vary.

Using prior knowledge, we can create the following dictionary:

```json
{
	"Adult": [18.5, 21.7, 24.3, 28.9, 30.5],
	"Senior": [23.4, 25.8, 27.6, 31.2, 33.9]
}
```

These lists provide typical BMI values for each target class. However, it's important to note that these values are arbitrary and should be interpreted with caution. The actual BMI ranges for classifying individuals into "Adult" or "Senior" age groups should be determined based on domain expertise or further analysis.