To quickly and directly answer the question: No, you should not add a scoring explanation to your survey. In doing so, you directly jeopardize the validity of the scores your customers are providing you.
When one of your customers receives your survey, you want their attention focused on providing their sincere sentiment as it relates to their overall experience with your product/service. By defining the parameters in which they answer, you’re shifting their attention to identifying themselves based on what they believe defines them. Consequently, you’ll influence the answer they give you, removing the validity of the survey.
Think about it from the standpoint of taking a personality test. If you were to ask, most people will confidently tell you their personality type … analytical, expressive, amiable, etc. However, often times these same people are surprised to learn that the results of a personality test don’t match their perceptions.
The same can be said with an NPS survey. Someone who gives you a 6 may define themselves as indifferent (or passive) to your brand. The reality is, they scored you a 6 for a reason, which means, whether they state it or not, they have a stronger degree of uncertainty for your brand than a 7 or an 8.
Now, had you defined passive as 7 or 8 beforehand, you likely would have influenced them to a higher score, which wouldn’t represent their true sentiment.
That said, just because you shouldn’t explain the scoring up front, doesn’t mean that you shouldn’t provide an explanation for the survey. In fact, at Promoter.io, we encourage it. Our research (over millions of surveys) has shown that providing a short introduction to your survey can increase your overall response rate.
An example from one of our clients, @mailchimp of such an intro would be:
If you have a minute, can you let us know how we’re doing? We read and value every single reply. (Seriously!)
And, when combined with the survey, it would look something like this: