When I was in school, a 7 out of 10 was good for a C - just barely passing. 8/10 - B, 9+/10 - A. A 6/10 is a D and 5/10 and below is an F.
I'll stay at a C short-term. I'll overnite at a D.
You and I both use the same system. I don't think I ever gave anyone a 10 because that basically denotes perfection with no need for any improvement at all. By the same token, I don't think I ever gave anyone less than a 3, because if it was less than that, I wouldn't have stayed there in the first place. Most of my reviews range from 6 (overnighter) to 9 (I'd probably buy a site if they were available).
Numeric scales tend to be useless, because aside from differing opinions, people interpret the numbers differently. Strictly speaking, a 5 would be an average place (while a dump would be a 0 or a 1), but I'd bet most people tend to view a 5 as very bad instead of average. IMO, it's better to gauge the quality of a CG from a textual review, just because of the inherent ambiguity of a single number.
Or as one reviewer I was TRYING to follow (all others had rated this campground with a 2 or 3, maybe a 4 at the highest. This reviewer gave the CG a 9! Then I read what he/she had to say - "worse campground I've stayed in in 15 years of camping. Would never return and on and on....." Yet, he/she gave them a 9 out of 10 with 10 being the highest (best). Go figure! How many times do you suppose that happens? I always read the "whys". Why is it rated so low (or high), and so on. We usually stick to state campgrounds - there is a degree of consistency to them. We know ahead of time exactly what to expect - elec. with no water and no sewer hook ups but always a filling place for water and dumping areas for the tanks. Usually clean and usually working toilets and showers. And usually well enforced quiet hours. Those things are important to us. We don't need a pool but we do like a roomy spot.
Have fun with your camping and keep reading those reviews!!!
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2007 25' Airstream International SS OB
2004 Nissan Armada
Equalizer hitch
Prodigy brake controls
"It's better to keep your mouth shut and thought a fool
Than to open it and remove all doubt."