To analyze the relationship between the feature RIDAGEYR (Respondent's Age) and the target variable (age group), we can make some assumptions based on prior knowledge.

Typically, the age group for seniors is considered to be 65 or older. Therefore, we can define "Senior" as RIDAGEYR values greater than or equal to 65.

For the non-senior or "Adult" category, we can consider individuals younger than 65. However, it would be helpful to define a reasonable range for adults. Let's consider 18 to 64 as the age range for adults.

Using this information, we can create a dictionary with typical RIDAGEYR values for each target class:

```json
{
    "Adult": [30.0, 45.0, 50.0, 55.0, 60.0],
    "Senior": [70.0, 75.0, 80.0, 85.0, 90.0]
}
```

Please note that these values are just examples and might not represent the actual distribution of RIDAGEYR values for each target class. They are provided based on assumptions made using prior knowledge.