Oh hell... sorry for the error Matt. I messed up the order of operations when aggregating some of the constants in the formula from what I worked out in Excel versus what I gave to you. The correct constant is 112.5, not 5.555555 (112.5 is 25*4.5, whereas I gave you 25/4.5).

So the correct formula is

Page score = 70 + 30 * [1-1/e^((x-5.5)*y/112.5)]

That should give the exact results of my examples.

To explain the constants:

5.5 in the formula is used to define a neutral vote (as Bob correctly explained). Thus a ten gets treated as a 4.5, a nine as a 3.5, a six as a 0.5, and a one as a -4.5 for example. This is why an eight counts about half as much to the score as a ten (actually 55% as much since 2.5/4.5 = 55%). A six counts 11% as much (0.5/4.5). And any vote under 5.5 is negative and starts lowering the score.

The other constant, 112.5 being the correct one (not 5.555555 anymore) is what affects how quickly scores increase. 112.5 is 25 * 4.5 and has the effect of increasing a page score by 4% of the remaining amount from the previous score towards the eventual goal of 100 for each 10 vote received (25 is 4% of 100 and 4.5 is the value of a 10). To increase scores faster... like 5% for each 10, use 20 * 4.5 = 90. For smaller changes with each vote the constant is increased (225 will increase scores 2% for each 10 and takes twice as many votes as the current formula). In picking a constant I tried to balance between the score not changing too rapidly if a bunch of 10s were given, but also changing enough to be noticed if only a few 7s and 8s were received.

This 112.5 constant can basically be anything depending on how much you want to change the score, but the above shows how to determine the value if you already have a desire in terms of what magnitude a single vote should result in.