A rating is a form of vote, but differs from traditional democratic voting in the following ways:
- There is a maximum of one rating per answer, rather than one rating per user; users may rate every answer, or any subset.
- Ratings can be negative (disapproval) as well as positive (approval)
- Ratings are on a scale (e.g. -10 to +10) rather than being binary (yes/no)
In other words, a rating is essentially a range vote.
For user friendliness, we might as well let users pick their own scale and simply normalize all ratings to a common scale before aggregating them.
Some people may not be comfortable with voting more complex than just indicating "yes/no", so possibly the default scale should be something simple like -1 to +1 (accompanied by clear verbal cues like "against" and "in favor") -- and just make sure the link to change your scale preference is easy to find.