Based on prior knowledge of blood insulin levels and their association with age, we can analyze how the feature LBXIN relates to the target variable of age group.

Observations:
1. In general, blood insulin levels tend to increase with age due to factors like reduced insulin sensitivity and increased insulin resistance.
2. There is a higher likelihood of higher blood insulin levels in senior individuals compared to non-senior individuals.

Based on this analysis, let's create the dictionary:

```json
{
	"Adult": [5.8, 8.3, 7.2, 6.6, 5.9],  
	"Senior": [10.2, 11.8, 9.5, 12.1, 11.2]
}
```

Please note that the specific values provided in the list are hypothetical and should be replaced with actual values based on the available data and analysis.