Standard Deviations of Test/Section Scores

Hey folks, I was curious as to the typical distribution of a test writer's scores. I am beginning to write full length PTs and i'm wondering how indicative they are of my true 'mean' score. For example, should i expect +/- 2, 3, or 4 etc.? I realize the answer to this is likely to be dependent on each individual person but I was wondering if anyone could offer insight.

Sam