Based on prior knowledge and common understanding of age groups, we can make some assumptions about the appropriate ranges of values for each target class.

For the 'Adult' age group, we can assume a range from around 18 years old to 64 years old. While there is no strict definition of when someone becomes a senior citizen, for the purpose of this analysis we can assume a 'Senior' age group starting from around 65 years old.

With this in mind, we can perform the analysis on the feature RIDAGEYR and generate the dictionary:

```json
{
	"Adult": [18.0, 25.0, 35.0, 45.0, 50.0],
	"Senior": [65.0, 70.0, 75.0, 80.0, 85.0]
}
```

Please note that this analysis is based on assumptions and general understanding. The specific definition of 'Adult' and 'Senior' age groups may vary in different contexts or datasets.