Based on my prior knowledge and analysis of the relationship between the "lug_boot" feature and the task of rating the decision to buy a car, here is the generated dictionary:

```json
{
	"unacceptable": ["small"],
	"acceptable": ["med"],
	"very good": ["big"],
	"good": ["med", "big"]
}
```

In this analysis, the "lug_boot" feature value of "small" is associated with a rating of "unacceptable". The value of "med" is associated with a rating of "acceptable" or "good", and the value of "big" is associated with a rating of "very good" or "good".

Please note that this analysis is based on general assumptions and may not cover all possible scenarios.