Strategic Statement: This is a very subjective question, and any numerical response would be near meaningless. Think creatively about how you can take a question like this and turn it to your advantage (making your response memorable).
Sample Response: No matter the project or the environment, I realize that I am a part of a team. As a part of a team, whatever ‘ethics rating’ I give myself is somewhat reliant on the ratings of others as well. So... let’s consider ourselves a team. I’ll give myself a ten, add to that the rating you give yourself and divide by two!