Based on prior knowledge, the number of doors can be a useful indicator to determine the decision to buy a car. Here is a thorough analysis of the relationship between the number of doors and the decision to buy the car:

1. Unacceptable: Cars with only 2 doors are more likely to be considered unacceptable for buying, as they might be less practical for everyday use or have limited space for passengers and cargo.

2. Acceptable: Cars with 3 doors might be considered acceptable for buying, although they are less common in the market. Some consumers might prefer the uniqueness and style of a car with 3 doors.

3. Good: Cars with 4 doors are generally considered good for buying. They provide easier access to the rear seats and accommodate more passengers and cargo.

4. Very Good: Cars with 5 doors or more are highly likely to be considered very good for buying. They offer the most convenience, space, and flexibility for passengers and cargo.

Based on this analysis, the dictionary would be as follows:

```json
{
	"unacceptable": ["2"],
	"acceptable": ["3"],
	"good": ["4"],
	"very good": ["5more"]
}
```