Based on the given description, we are trying to predict whether a person is in the senior age group or not based on their engagement in moderate or vigorous-intensity sports, fitness, or recreational activities in a typical week. The feature PAQ605 represents this engagement, where 1 indicates participation and 2 indicates non-participation.

To analyze the relationship between the feature and the task, we can make some assumptions based on prior knowledge:

1. Since the task is to predict whether a person is a senior or not, it is reasonable to assume that older individuals may be less engaged in moderate or vigorous-intensity physical activities compared to younger individuals. Hence, we might expect to see a higher proportion of '2' values for seniors.
2. It is also possible that there may be seniors who are still actively participating in such activities, so we should not completely disregard the possibility of '1' values for seniors.

Now, let's create the dictionary containing the possible values of feature PAQ605 for each target class:

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

Here, we have included 5 possible values for each target class ('Adult' and 'Senior'). Note that these are just example values based on the assumptions made, and in a real analysis, we would need more data and statistical techniques to make more accurate conclusions.