Based on prior knowledge, we can assume that a person is classified as a senior if their age is 65 or above, and as an adult if their age is below 65.

After analyzing the relationship between the feature RIDAGEYR and the target task of predicting age group, the dictionary can be generated as follows:

```json
{
	"Adult": [20.0, 42.0, 30.0, 47.0, 50.0],
	"Senior": [70.0, 68.0, 75.0, 80.0, 82.0]
}
```

In this dictionary, the "Adult" key corresponds to the possible values of the feature RIDAGEYR for the target class "Adult", while the "Senior" key corresponds to the possible values of the feature RIDAGEYR for the target class "Senior". The RIDAGEYR values are presented as floats in the respective lists.