The purpose of the Site Self-Evaluation is to be a bit introspective — to step back and capture periodic snapshots of how the site looks from the outside (the Internet) looking in. It's easy to get caught up in the daily rigamarole of 'questions per day', reputation, and 'percent answered', but it's important on occasion to take a step back to see the forest for the trees — how is this site doing in this subject space?
I petitioned hard to keep this a site self-examination. The respondents should be representative of the broader community; as broad as possible. The more participants, the better.
Personally, I'm not nearly as interested in the number of 'better, worse, or same' ratings given, inasmuch as what communities DO with that information. What activities and discussion are generated around what you discovered, if anything? Are there broader issues that can be addressed? Or at the very very least, are the problems uncovered by the sample questions even fixed… or is the community generally content with the status quo?
No two community evaluations are alike, nor can they be used as a basis for comparison. It is impossible to assign an objective pass/fail grade based on the numerical results; and that is entirely besides the point. The purpose is to step back from all the analytics and take a look at the "essay portion" of the work you are doing here — how does the site perform from the outside looking in? Where do you fit in among the other sites covering this address space?
What you should expect to get from these surveys and what you plan to do with it is entirely up to you. Not to be too evasive, but that's sort of the point of a self-evaluation.