Our own TonyTonyChopper did a bunch of statistics on this for SDNers. He found that, on average, people score +/- 1.88 points higher or lower than their AAMC practice exam average. There are a few 6+ point drops and a few 6+ point gains, but these are very rare, - maybe 1 out of 50 applicants.
Yes, 55 people out of the sample population gave me both their AAMC average and actual MCAT score. Out of those 55, we had a range of -4 to +5.8 difference from their AAMC average. Three people scored -4, two people +4, one -5, one +5, and one +5.8. Though be verrrry cautious interpreting these numbers due to the self-reporting bias. These observations are probably only externally valid for individuals who actively participate and post in the SDN community. Not the lurkers. As you can see:
The average MCAT score for 71 people was 32.1 (stdev 4.5) for us, SDNers
And I forget how many, but there was a small group of people who were actively participating in the thread, but once the scores came out, they dissappeared and others explicitely stated that their scores were low to post (by their standards...I suspect some were like a 30, but they were expecting a 35+...).
I would still say it's quite rare for someone to score >= 6 points, especially 10 points (lower or higher), from their AAMC average -
contingent on they did the practice tests the way they were supposed to be taken. If you
retake a practice exam or don't take them like a real exam (like my friend who got up to do something else between every verbal passage), then expect a lower score.
On average, people scored +/- 1.88 points from their AAMC average with a standard deviation of 1.45.
