Analyzing the relationship between the feature RIDAGEYR and the task of predicting the person's age group, we can make some assumptions based on prior knowledge.

Typically, senior citizens are considered to be individuals who are 65 years of age or older. Therefore, we can define Senior as RIDAGEYR values greater than or equal to 65. Conversely, non-senior or Adult can be defined as RIDAGEYR values less than 65.

Based on this analysis, the dictionary can be created as follows:

```json
{
	"Adult": [18.0, 30.0, 40.0, 50.0, 60.0],
	"Senior": [65.0, 70.0, 75.0, 80.0, 90.0]
}
```
Note: The provided RIDAGEYR values are for illustrative purposes only and may not represent the actual distribution of data.