Based on prior knowledge, the analysis of the relationship between the LBXIN feature and the age group target can be done as follows:

1. Adult: Generally, insulin levels tend to be lower in adults. Therefore, we would expect lower LBXIN values for the Adult age group.

2. Senior: As individuals age, insulin resistance may increase, resulting in higher insulin levels. Therefore, we would expect higher LBXIN values for the Senior age group.

Based on this analysis, let's create the dictionary with typical LBXIN values for each target class:

```json
{
    "Adult": [8.5, 9.3, 7.8, 9.2, 8.1],
    "Senior": [12.6, 11.9, 13.4, 12.1, 11.3]
}
```

Please note that the exact ranges of LBXIN values for each age group may vary depending on the specific dataset and population being analyzed.