Based on prior knowledge, I will assume that the age group to determine if someone is a senior or not is defined by a specific age threshold such as 60 or 65 years old.

To analyze the relationship between the feature 'RIAGENDR' (Respondent's Gender) and the task of predicting age group, we need to identify the typical values of 'RIAGENDR' for each target class ('Adult' and 'Senior').

Here is the dictionary with typical 'RIAGENDR' values for each target class:

```json
{
    "Adult": [1.0, 2.0, 1.0, 1.0, 2.0],
    "Senior": [2.0, 2.0, 1.0, 2.0, 1.0]
}
```

Please note that the typical 'RIAGENDR' values provided above are examples and may not accurately represent the actual relationship between the feature and target in your dataset. It is recommended to perform a thorough analysis of the data to validate these findings.