Analysis:

To analyze the relationship between the "RIAGENDR" feature and the target of predicting age group (senior or non-senior), we can look at the typical age distributions among males and females. 

Based on prior knowledge, we can assume that the age range for seniors is typically higher compared to non-seniors. Therefore, we can hypothesize that there might be differences in the distribution of gender within the two age groups.

To create the dictionary, we will determine typical values of the "RIAGENDR" feature for each target class:

Dictionary:

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

Please note that the values in the lists are based on assumed typical gender proportions for the target classes. These values could change depending on the specific dataset and analysis conducted.